Cytoscape.js 2.0.3
A JavaScript graph library for analysis and visualisation (compatible with CommonJS/Node.js, jQuery 1.4+, and plain JavaScript)
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This is how easy it is to get started with Cytoscape.js (this code creates the instance you see on the bottom-right:

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    $(loadCy = function(){

      options = {
        showOverlay: false,
        minZoom: 0.5,
        maxZoom: 2,

        style: cytoscape.stylesheet()
          .selector('node')
            .css({
              'content': 'data(name)',
              'font-family': 'helvetica',
              'font-size': 14,
              'text-outline-width': 3,
              'text-outline-color': '#888',
              'text-valign': 'center',
              'color': '#fff',
              'width': 'mapData(weight, 30, 80, 20, 50)',
              'height': 'mapData(height, 0, 200, 10, 45)',
              'border-color': '#fff'
            })
          .selector(':selected')
            .css({
              'background-color': '#000',
              'line-color': '#000',
              'target-arrow-color': '#000',
              'text-outline-color': '#000'
            })
          .selector('edge')
            .css({
              'width': 2,
              'target-arrow-shape': 'triangle'
            })
        ,

        elements: {
          nodes: [
            {
              data: { id: 'j', name: 'Jerry', weight: 65, height: 174 }
            },

            {
              data: { id: 'e', name: 'Elaine', weight: 48, height: 160 }
            },

            {
              data: { id: 'k', name: 'Kramer', weight: 75, height: 185 }
            },

            {
              data: { id: 'g', name: 'George', weight: 70, height: 150 }
            }
          ],

          edges: [
            { data: { source: 'j', target: 'e' } },
            { data: { source: 'j', target: 'k' } },
            { data: { source: 'j', target: 'g' } },

            { data: { source: 'e', target: 'j' } },
            { data: { source: 'e', target: 'k' } },

            { data: { source: 'k', target: 'j' } },
            { data: { source: 'k', target: 'e' } },
            { data: { source: 'k', target: 'g' } },

            { data: { source: 'g', target: 'j' } }
          ],
        },

        ready: function(){
          cy = this;
        }
      };

      $('#cy').cytoscape(options);

    });

# Introduction

## About

Cytoscape.js is an open-source graph library written in JavaScript. You can use Cytoscape.js for graph analysis and visualisation.

Cytoscape.js allows you to easily display graphs in your websites. Because Cytoscape.js allows the user to interact with the graph and the library allows the client to hook into user events, Cytoscape.js is easily integrated into your webapp, especially since Cytoscape.js supports both desktop browsers, like Chrome, and mobile browsers, like on the iPad.

Cytoscape.js also has graph analysis in mind: The library contains a slew of useful functions in graph theory. You can use Cytoscape.js headlessly on Node.js to do graph analysis in the terminal or on a web server.

The library was developed at the Donnelly Centre at the University of Toronto. It is the successor of Cytoscape Web.

## Cytoscape.js & Cytoscape

Though Cytoscape.js shares its name with Cytoscape, Cytoscape.js is not Cytoscape. Cytoscape.js is a JavaScript library for programmers. It is not an app for end-users, nor can you just copy-paste some code to "automagically" make you a webapp.

Cytoscape.js is a JavaScript library: It gives you a reusable graph widget that you can integrate with the rest of your webapp with your own JavaScript code. The keen members of the audience will point out that this means that Cytoscape plugins — written in Java — will obviously not work in Cytoscape.js — written in JavaScript.

We are trying to make the two projects intercompatible as possible, and we do share philosophies with Cytoscape: Graph style and data should be separate, the library should provide core functionality with extensions adding functionality on top of the library, and so on.

## Funding

Funding for Cytoscape.js and Cytoscape is provided by NRNB (U.S. National Institutes of Health, National Center for Research Resources grant numbers P41 RR031228 and GM103504) and by NIH grants 2R01GM070743 and 1U41HG006623. The following organizations help develop Cytoscape:

ISB | UCSD | MSKCC | Pasteur | Agilent | UCSF | Unilever | Toronto | NCIBI

# Roadmap

Plans for future versions of Cytoscape.js can be found on the issue tracker.

# Notation

## Architecture & API

There are two components in the architecture that a developer need concern himself in order to use Cytoscape.js, the core and the collection. In Cytoscape.js, the core is a developer's main entry point into the library. From the core, a developer can run layouts, alter the viewport, and perform other operations on the graph as a whole.

The core provides several functions to access elements in the graph. Each of these functions returns a collection, a set of elements in the graph. A set of functions are available on collections that allow the developer to filter the collection, perform operations on the collection, traverse the graph about the collection, get data about elements in the collection, and so on.

## Notation

There are several types that different functions can be executed on, and the variable names used to denote these types in the documentation are outlined below:

    Notation       Works on
    --------       --------
    cy ........... the core
    eles ......... a collection of one or more elements (nodes and edges)
    ele .......... a collection of a single element (node or edge)
    nodes ........ a collection of one or more nodes
    node ......... a collection of a single node
    edges ........ a collection of one or more edges
    edge ......... a collection of a single edge

By default, a function returns a reference back to the calling object to allow for jQuery-like chaining (e.g. `obj.fn1().fn2().fn3()`). Unless otherwise indicated in this documentation, a function is chainable in this manner unless a different return value is specified. This applies both to the core and to collections.

For functions that return a value, note that calling a singular — `ele`, `node`, or `edge` — function on a collection of more than one element will return the expected value for only the first element.

## Position

There is an important distinction to make for position: A position may be a model position or a rendered position.

A model position — as its name suggests — is the position stored in the model for an element. An element's model position remains constant, despite changes to zoom and pan.

A rendered position is an on-screen location relative to the viewport. For example, a rendered position of `{ x: 100, y: 100 }` specifies a point 100 pixels to the right and 100 pixels down from the top-left corner of the viewport. An element's rendered position naturally changes as zoom and pan changes, because the element's on-screen position in the viewport changes as zooming and panning are applied.

In this documentation, "position" refers to model position unless otherwise stated.

## Elements JSON

Examples are given that outline format of the elements JSON used to load elements into Cytoscape.js:

    $('#cy').cytoscape({

      elements: [
        { // node n1
          group: 'nodes', // 'nodes' for a node, 'edges' for an edge

          data: { // element data (put dev data here)
              id: 'n1', // mandatory for each element, assigned automatically on undefined
              parent: 'nparent', // indicates the compound node parent id; not defined => no parent
          },

          position: { // the model position of the node (optional on init, mandatory after)
              x: 100,
              y: 100
          },

          selected: false, // whether the element is selected (default false)

          selectable: true, // whether the selection state is mutable (default true)

          locked: false, // when locked a node's position is immutable (default false)

          grabbable: true, // whether the node can be grabbed and moved by the user

          classes: 'foo bar' // a space separated list of class names that the element has
        },

        { // node n2
          group: 'nodes',
          data: { id: 'n2' },
          renderedPosition: { x: 200, y: 200 } // can alternatively specify position in rendered on-screen pixels
        },

        { // node n3
          group: 'nodes',
          data: { id: 'n3', parent: 'nparent' },
          position: { x: 123, y: 234 }
        },

        { // node nparent
          group: 'nodes',
          data: { id: 'nparent' }
        },

        { // edge e1
          group: 'edges',
          data: {
              id: 'e1',
              source: 'n1', // the source node id (edge comes from this node)
              target: 'n2'  // the target node id (edge goes to this node)
          }
        }
      ],

      // so we can see the ids
      style: [
        {
          selector: 'node',
          css: {
            'content': 'data(id)'
          }
        }
      ]

    });

# Selectors

## Notes & caveats

A selector functions similar to a jQuery selector on DOM elements, but selectors in Cytoscape.js instead work on collections.

The selectors can be combined together to make powerful queries in Cytoscape.js, for example:

    // get all nodes with weight more than 50 and height strictly less than 180
    cy.elements("node[weight >= 50][height < 180]");

Selectors can be joined together (effectively creating a logical OR) with commas:

    // get node j and the edges coming out from it
    cy.elements("node#j, edge[source = 'j']");

It is important to note that strings need to be enclosed by quotation marks:

    //cy.filter("node[name = Jerry]"); // this doesn't work
    cy.filter("node[name = 'Jerry']"); // but this does

## Group, class, & ID

`node`, `edge`, or `*` (group selector) Matches elements based on group (`node` for nodes, `edge` for edges, `*` for all).

`.className` Matches elements that have the specified class (e.g. use `.foo` for a class named "foo").

`#id` Matches element with the matching ID (e.g. `#foo` is the same as `[id = 'foo']`)

## Data

`[name]`
Matches elements if they have the specified data attribute defined aka not `undefined` (e.g. `[foo]` for an attribute named "foo"). Here, `null` is considered a defined value.

`[?name]`
Matches elements if the specified data attribute is a truthy value (e.g. `[?foo]`).

`[!name]`
Matches elements if the specified data attribute is a falsey value (e.g. `[!foo]`).

`[^name]`
Matches elements if the specified data attribute is not defined aka `undefined` (e.g `[^foo]`). Here, `null` is considered a defined value.

`[name = value]`
Matches elements if their data attribute matches a specified value (e.g. `[foo = 'bar']` or `[num = 2]`).

`[name != value]`
Matches elements if their data attribute doesn't match a specified value (e.g. `[foo != 'bar']` or `[num != 2]`).

`[name > value]`
Matches elements if their data attribute is greater than a specified value (e.g. `[foo > 'bar']` or `[num > 2]`).

`[name >= value]`
Matches elements if their data attribute is greater than or equal to a specified value (e.g. `[foo >= 'bar']` or `[num >= 2]`).

`[name < value]`
Matches elements if their data attribute is less than a specified value (e.g. `[foo < 'bar']` or `[num < 2]`).

`[name <= value]`
Matches elements if their data attribute is less than or equal to a specified value (e.g. `[foo <= 'bar']` or `[num <= 2]`).

`[name *= value]`
Matches elements if their data attribute contains the specified value as a substring (e.g. `[foo *= 'bar']`).

`[name ^= value]`
Matches elements if their data attribute starts with the specified value (e.g. `[foo ^= 'bar']`).

`[name $= value]`
Matches elements if their data attribute ends with the specified value (e.g. `[foo $= 'bar']`).

`@` (data attribute operator modifier)
Prepended to an operator so that is case insensitive (e.g. `[foo @$= 'ar']`, `[foo @>= 'a']`, `[foo @= 'bar']`)

`{}` (metadata brackets)
Use curly brackets in place of square ones to match against metadata instead of data (e.g. `{degree > 2}` matches elements of degree greater than 2). The properties that are supported include `degree`, `indegree`, and `outdegree`.

## Compound nodes

`>` (child selector)
Matches direct children of the parent node (e.g. `node > node`).

`` (descendant selector)
Matches descendants of the parent node (e.g. `node node`).

`$` (subject selector)
Sets the subject of the selector (e.g. `$node > node` to select the parent nodes instead of the children).

## State

Animation

- `:animated` : Matches elements that are currently being animated.
- `:unanimated` : Matches elements that are not currently being animated.

Selection

- `:selected` : Matches selected elements.
- `:unselected` : Matches elements that aren't selected.
- `:selectable` : Matches elements that are selectable.
- `:unselectable` : Matches elements that aren't selectable.

Locking

- `:locked` : Matches locked elements.
- `:unlocked` : Matches elements that aren't locked.

Visibility

- `:visible` : Matches elements that are visible.
- `:hidden` : Matches elements that are hidden.

User interaction:

- `:grabbed` : Matches elements that are being grabbed by the user.
- `:free` : Matches elements that are not currently being grabbed by the user.
- `:grabbable` : Matches elements that are grabbable by the user.
- `:ungrabbable` : Matches elements that are not grabbable by the user.
- `:active` : Matches elements that are active (i.e. user interaction, similar to `:active` in CSS).
- `:inactive` : Matches elements that are inactive (i.e. no user interaction).
- `:touch` : Matches elements when displayed in a touch-based enviroment (e.g. on a tablet).

In or out of graph

- `:removed` : Matches elements that have been removed from the graph.
- `:inside` : Matches elements that have are in the graph (they are not removed).

Compound nodes

- `:parent` : Matches parent nodes (they have one or more child nodes).
- `:child` : Matches child nodes (they each have a parent).

# Style

Style in Cytoscape.js follows CSS conventions as closely as possible. In most cases, a property has the same name and behaviour as its corresponding CSS namesake. However, the properties in CSS are not sufficient to specify the style of some parts of the graph. In that case, additional properties are introduced that are unique to Cytoscape.js.

It is important to note that in your stylesheet, specificity rules are completely ignored. In CSS, specificity often makes stylesheets behave in ways contrary to developer's natural mental model. This is terrible, because it wastes time and overcomplicates things. Thus, there is no analogue of CSS specificity in Cytoscape.js stylesheets. For a given style property for a given element, the last matching selector wins. In general, you should be using something along the lines of OOCSS principles, anyway — making specificity essentially irrelevant.

## Format

The style specified at initialisation can be in a functional format or in a plain JSON format, the plain JSON format being more useful if you want to pull down the style from the server.

### Plain JSON format

    $('#cy').cytoscape({
      // ...

      style: [
        {
          selector: 'node',
          css: {
            'background-color': 'red'
          }
        }

        // , ...
      ]

      // , ...
    });

### Functional format

    $('#cy').cytoscape({
      // ...

      style: cytoscape.stylesheet()
        .selector('node')
          .css({
            'background-color': 'blue'
          })

          // ...

      // , ...
    });

## Properties

### Notes

- Colours may be specified by name (e.g. `red`), hex (e.g. `#ff0000` or `#f00`), RGB (e.g. `rgb(255, 0, 0)`), or HSL (e.g. `hsl(0, 100%, 50%)`).
- Values requiring a number, such as a length, can be specified in pixel values (e.g. `24px`), unitless values that are implicitly in pixels (`24`), or em values (e.g. `2em`).
- Opacity values are specified as numbers ranging on `0 <= opacity <= 1`.

### Element properties

These properties can be used on any element.

Labels:

- `color` : The colour of the element's label.
- `content` : The text to display for an element's label.
- `font-family` : A comma-separated list of font names to use on the label text.
- `font-size` : The size of the label text.
- `font-style` : A CSS font style to be applied to the label text.
- `font-weight` : A CSS font weight to be applied to the label text.
- `text-opacity` : The opacity of the label text, including its outline.
- `text-outline-color` : The colour of the outline around the element's label text.
- `text-outline-opacity` : The opacity of the outline on label text.
- `text-outline-width` : The size of the outline on label text.

Size & visibility:

- `opacity` * : The opacity of the element.
- `visibility` : Whether the element is visible; can be `visible` or `hidden`.
- `width` : The element's width; the line width for edges or the horizontal size of a node.
- `z-index` : A non-negative integer that specifies the z-ordering of the element. An element with a higher `z-index` is put on top of an element with a lower value.

For overlays (e.g. used in `:active` state):

- `overlay-color` : The colour of the overlay.
- `overlay-padding` : The area outside of the element within which the overlay is shown.
- `overlay-opacity` : The opacity of the overlay.

### Node properties

These properties apply only to nodes.

Labels:

- `text-halign` : The vertical alignment of a label; may have value `left`, `center`, or `right`.
- `text-valign` : The vertical alignment of a label; may have value `top`, `center`, or `bottom`.

Body:

- `background-image` : The URL that points to the image that should be used as the node's background.
- `background-color` : The colour of the node's body.
- `background-opacity` : The opacity level of the node's body.
- `border-color` : The colour of the node's border.
- `border-opacity` : The opacity of the node's border.
- `border-width` : The size of the node's border.
- `height` : The height of the node's body.
- `shape` : The shape of the node's body; may be `rectangle`, `roundrectangle`, `ellipse`, `triangle`, `pentagon`, `hexagon`, `heptagon`, `octagon`.

Compound nodes:

- `padding-left` : The size of the area on the left of the compound node that can not be occupied by child nodes.
- `padding-right` : The size of the area on the right of the compound node that can not be occupied by child nodes.
- `padding-top` : The size of the area on the top of the compound node that can not be occupied by child nodes.
- `padding-bottom` : The size of the area on the bottom of the compound node that can not be occupied by child nodes.

### Edge properties

These properties apply only to edges:

- `line-color` : The colour of the edge's line.
- `line-style` : The style of the edge's line; may be `solid`, `dotted`, or `dashed`.
- `source-arrow-color` : The colour of the edge's arrow on the source side.
- `source-arrow-shape` : The shape of the edge's arrow on the source side; may be `tee`, `triangle`, `square`, `circle`, `diamond`, or `none`.
- `target-arrow-color` : The colour of the edge's arrow on the target side.
- `target-arrow-shape` : The shape of the edge's arrow on the target side; may be `tee`, `triangle`, `square`, `circle`, `diamond`, or `none`.

### Core properties

These properties apply only to the core. You can use the special `core` selector string to set these properties.

- `active-bg-color` : The colour of the indicator shown when the background is grabbed by the user.
- `active-bg-opacity` : The opacity of the active background indicator.
- `active-bg-size` : The size of the active background indicator.
- `selection-box-color` : The background colour of the selection box used for drag selection.
- `selection-box-border-color` : The colour of the border on the selection box.
- `selection-box-border-width` : The size of the border on the selection box.
- `selection-box-opacity` : The opacity of the selection box.

## Mappers

In addition to specifying the value of a property outright, the developer may also use a mapper to dynamically specify the property value.

`data()` specifies a direct mapping to an element's data field. For example, `data(descr)` would map a property to the value in an element's `descr` field in its data (i.e. `ele.data("descr")`). This is useful for mapping to properties like label text content (the `content` property).

`mapData()` specifies a linear mapping to an element's data field. For example, `data(weight, 0, 100, blue, red)` maps an element's weight to gradients between blue and red for weights between 0 and 100. An element with `ele.data("weight") === 0` would be mapped to blue, for instance. Elements whose values fall outside of the specified range are mapped to the extremity values. In the previous example, an element with `ele.data("weight") === -1` would be mapped to blue.

# Events

## Event object

Events passed to handler callbacks are jQuery-event-like objects. They have an additional field named `cyTarget`, which indicates the element or core that first caused the event.

## Event bubbling

All events that occur on elements get bubbled up to the core. You must take this into consideration when binding to the core so you can differentiate between events that happened on the background and ones that happened on elements. Use the `eventObj.cyTarget` field, which indicates the originator of the event (i.e. `eventObj.cyTarget === cy || eventObj.cyTarget === someEle`).

## User input device events

These are normal browser events that you can bind to via Cytoscape.js. You can bind these events to the core and to collections.

- `mousedown` : when the mouse button is pressed
- `mouseup` : when the mouse button is released
- `click` : after `mousedown` then `mouseup`
- `mouseover` : when the cursor is put on top of the target
- `mouseout` : when the cursor is moved off of the target
- `mousemove` : when the cursor is moved somewhere on top of the target
- `touchstart` : when one or more fingers starts to touch the screen
- `touchmove` : when one or more fingers are moved on the screen
- `touchend` : when one or more fingers are removed from the screen

There are also some higher level events that you can use so you don't have to bind to different events for mouse-input devices and for touch devices.

- `tapstart` or `vmousedown` : normalised tap start event (either `mousedown` or `touchstart`)
- `tapend` or `vmouseup` : normalised tap end event (either `mouseup` or `touchend`)
- `tap` or `vclick` : normalised tap event (either `click`, or `touchstart` followed by `touchend` without `touchmove`)
- `taphold` : normalised tap hold event
- `cxttapstart` : normalised right-click mousedown or two-finger `tapstart`
- `cxttapend` : normalised right-click `mouseup` or two-finger `tapend`
- `cxttap` : normalised right-click or two-finger `tap`
- `cxtdrag` : normalised mousemove or two-finger drag after `cxttapstart` but before `cxttapend`

## Collection events

These events are custom to Cytoscape.js. You can bind to these events for collections.

- `add` : when an element is added to the graph
- `remove` : when an element is removed from the graph
- `select` : when an element is selected
- `unselect` : when an element is unselected
- `lock` : when an element is locked
- `unlock` : when an element is unlocked
- `grab` : when an element is grabbed by the mouse cursor or a finger on a touch input
- `drag` : when an element is grabbed and then moved
- `free` : when an element is freed (i.e. let go from being grabbed)
- `position` : when an element changes position
- `data` : when an element's data is changed
- `style` : when an element's style is changed

## Graph events

These events are custom to Cytoscape.js, and they occur on the core.

- `layoutstart` : when a layout starts running
- `layoutready` : when a layout has set positions for all the nodes
- `layoutstop` : when a layout has finished running completely or otherwise stopped running
- `load` : when a new graph is loaded via initialisation or `cy.load()`
- `ready` : when a new instance of Cytoscape.js is ready to be interacted with
- `initrender` : when the first frame is drawn by the renderer (useful for synchronising with image exports etc)
- `done` : when a new instance of Cytoscape.js is ready to be interacted with and its initial layout has finished running
- `pan` : when the viewport is panned
- `zoom` : when the viewport is zoomed

# Core

The core object is your interface to the Cytoscape.js visualisation. It is your entry point to Cytoscape.js: All of Cytoscape.js's features are accessed through this object.

## Initialisation

### Script includes

To use Cytoscape.js in your HTML document:

    <script src="cytoscape.js"></script>

To use Cytoscape.js in a CommonJS environment like Node.js:

    var cytoscape = require('cytoscape');

### Getting started

An instance of Cytoscape.js correponds to a graph. You can create an instance as follows:

    cytoscape({
      container: document.getElementById('cy'),
      ready: function(){ console.log('ready') }
    });

If you are running Cytoscape.js in Node.js or otherwise running it headlessly, you will not specify the `container` option.

If you've included jQuery on a HTML document, you can alternatively initialise Cytoscape.js on a HTML DOM element using the traditional jQuery style:

    $("#cy").cytoscape({ // for some div with id 'cy'
      ready: function(){
        // you can access the core object API through cy

        console.log("ready");
      }

      // , ...
    });

This initialises Cytoscape.js and returns back to you your instance of jQuery. You can continue using jQuery functions, as usual for a jQuery plugin.

For example,

    $("#cy").cytoscape(options)
      .css("background", "red")
      .css("border-color", "black"); // can use jquery functions on 'cy' div

Because this style doesn't give you access to the `cy` object outside of the callback function, there is an option to get the `cy` object from a jQuery selector.

    $("#cy").cytoscape(options);
    var cy = $("#cy").cytoscape("get"); // now we have a global reference to `cy`

### The ready callback

All of your code that uses the core object API, i.e. through the `cy` object in the examples above, must do so after the `ready` callback function has executed. You can specify the `ready` callback in the initialisation options, outlined in the following section.

Because the `ready` event may occur before you can bind to the core, you can use this shortcut to spread your code among several JavaScript files without having to call a bunch of global functions in `options.ready`.

NB: You should never call layouts, load elements into the graph, etc on ready. The graph is still performing the initial load at that point, so you can't modify things like that. You should use the initialisation options to properly set the elements and layout you want to use.

    // in foo.js
    $(function(){ // on jquery ready

      $("#cy").cytoscape(function(eventObject){ // on Cytoscape.js ready on the `cy` div
        // this code executes when Cytoscape.js is ready even though we
        // don't actually initialise Cytoscape.js on the `cy` div until
        // bar.js is loaded

        var cy = this; // `this` holds the reference to the core object

        console.log("Ready, Freddie!");
      });

    });

    // in bar.js (should be after foo.js in your js includes)
    $(function(){ // on jquery ready
      $("#cy").cytoscape(options);
    });

### Initialisation options

An instance of Cytoscape.js has a number of options that can be set on initialisation. They are outlined below.

    $("#cy").cytoscape({
      showOverlay: false,
      layout: { /* ... */ },
      zoom: 1,
      minZoom: 1e-50,
      maxZoom: 1e50,
      pan: { x: 0, y: 0 },
      renderer: { /* ... */ },
      style: undefined /* ... */,
      ready: function(evt){ /* ... */ },
      initrender: function(evt){ /* ... */ },
      elements: [ /* ... */ ]
    });

`layout` : A plain object that specifies layout options. Which layout is initially run is specified by the `name` field. Refer to a layout's documentation for the options it supports, as described in `cy.layout()`.

`zoom` : The initial zoom level of the graph. Make sure to disable viewport manipulation options, such as `fit`, in your layout so that it is not overridden when the layout is applied. You can set `options.minZoom` and `options.maxZoom` to set restrictions on the zoom level.

`pan` : The initial panning position of the graph. Make sure to disable viewport manipulation options, such as `fit`, in your layout so that it is not overridden when the layout is applied.

`renderer` : A plain object containing options for the renderer to be used. The `options.renderer.name` field specifies which renderer is used. You need not specify anything for the `renderer` option, unless you want to specify one of the rendering options below:

- `renderer.name` : The name of the renderer to use. By default, the `'canvas'` renderer is used. If you build and register your own renderer, then you can specify its name here.
- `renderer.hideEdgesOnViewport` : When set to `true`, the renderer does not render edges while the viewport is being manipulated. This makes panning and zooming more responsive for large graphs.

`style` : The stylesheet used to style the document.

For example:

    $("#cy").cytoscape({
      /* ... */

      style: cytoscape.stylesheet()
        .selector('node')
          .css({
            'background-color': 'red',
            'border-color': '#ffff00'
          })
        .selector('edge')
          .css({
            'line-color': 'blue'
          })

      /* ... */
    });

`ready` : A callback function that is called when Cytoscape.js is ready to be interacted with. You can not call functions on the `cy` object before this function executes.

`initrender` : A callback function that is called when Cytoscape.js has rendered its first frame. This is useful for grabbing screenshots etc after initialision, but in general you should use `ready` instead.

`showOverlay` : A boolean, indicating whether you'd like to see the "cytoscape.js" overlay in the bottom right of the viewport (default `true`).

`elements` : An array of elements specified as plain objects.

For example:

    $('#cy').cytoscape({
      /* ... */

      elements: [
        {
          data: { id: 'foo' },
          group: 'nodes'
        },

        {
          data: { id: 'bar' },
          group: 'nodes'
        },

        {
          data: { weight: 100 }, // elided id => autogenerated id
          group: 'nodes',
          position: {
            x: 100,
            y: 100
          },
          classes: 'className1 className2',
          selected: true,
          selectable: true,
          locked: true,
          grabbable: true
        },

        {
          data: { id: 'baz', source: 'foo', target: 'bar' },
          group: 'edges'
        }
      ]

      /* ... */
    });

You can alternatively specify separate arrays indexed in a object by the group names so you don't have to specify the `group` property over and over for each element:

    $('#cy').cytoscape({
      /* ... */

      elements: {
        nodes: [
          { data: { id: 'foo' } }, // NB no group specified

          { data: { id: 'bar' } },

          {
            data: { weight: 100 }, // elided id => autogenerated id
            group: 'nodes',
            position: {
              x: 100,
              y: 100
            },
            classes: 'className1 className2',
            selected: true,
            selectable: true,
            locked: true,
            grabbable: true
          }
        ],

        edges: [
          { data: { id: 'baz', source: 'foo', target: 'bar' } } // NB no group specified
        ]
      }

      /* ... */
    });

## Graph manipulation

cy.add()
Add elements to the graph and return them.
cy.add( , eleObj )
Add a specified element to the graph.

- eleObj A plain object that specifies the element.

cy.add( , eleObjs )
Add the specified elements to the graph.

- eleObjs An array of elements specified by plain objects.

cy.add( , eles )
Add the specified elements to the graph.

- eles A collection of elements.

### Details

If plain element objects are used, then the same format used at initialisation must be followed. It is important to note that the `group` attribute must be specified for plain objects, as this function can not infer whether the elements added are nodes or edges.

It is important to note that the positions of newly added nodes must be defined when calling `cy.add()`. Nodes can not be placed in the graph without a valid position — otherwise they could not be displayed.

NB: If a collection of existing elements is specified, then copies of those elements are added, which allows for elements to be effectively transferred between instances of Cytoscape.js. If you want to add removed elements back to the graph, use `eles.restore()` instead.

### Examples

Add a node from a plain object.

    cy.add({
        group: "nodes",
        data: { weight: 75 },
        position: { x: 200, y: 200 }
    });

Add nodes and edges to the graph as plain objects:

    // can use reference to eles later
    var eles = cy.add([
      { group: "nodes", data: { id: "n0" }, position: { x: 100, y: 100 } },
      { group: "nodes", data: { id: "n1" }, position: { x: 200, y: 200 } },
      { group: "edges", data: { id: "e0", source: "n0", target: "n1" } }
    ]);

cy.remove()
Remove elements from the graph and return them.
cy.remove( , eles )
Remove the specified elements.

- eles A collection of elements to remove.

cy.remove( , selector )
Remove elements in the graph matching the specified selector.

- selector Elements matching this selector are removed.

### Details

Though the elements specified to this function are removed from the graph, they may still exist in memory. However, almost all functions will not work on removed elements. For example, the `eles.neighborhood()` function will fail for a removed element: An element outside of the context of the graph can not have a neighbourhood defined. In effect, removed elements just exist so you can restore them back to the originating core instance or to a new instance.

### Examples

Remove an element:

    var j = cy.$("#j");
    cy.remove( j );

Remove a collection:

    var collection = cy.elements("node[weight > 50]");
    cy.remove( collection );

Remove elements matching a selector:

    cy.remove("node[weight > 50]"); // remove nodes with weight greater than 50

cy.load()
Load a graph.
cy.load( , eleObjs [, load] [, done] )

- eleObjs An array of plain objects that specify the elements to load.
- load A callback function called when the graph has loaded.
- done A callback function called after the graph is loaded and just after the layout finishes.

### Details

Note that `eleObjs` can be specified as an array with each element specifying its `group`, or alternatively, `eleObjs` can be specified as a `group`-indexed map, following the same format as in initialisation and outlined in the element JSON format.

### Examples

As an array:

    cy.load([
      { data: { id: "n1" }, group: "nodes" },
      { data: { id: "n2" }, group: "nodes" },
      { data: { id: "e1", source: "n1", target: "n2" }, group: "edges" }
    ]);

As a `group`-indexed map:

    cy.load({
      nodes: [
        { data: { id: "n1" } },
        { data: { id: "n2" } }
      ],

      edges: [
        { data: { id: "e1", source: "n1", target: "n2" } }
      ]
    });

With specified callbacks:

    cy.load([ { data: { id: "n1" }, group: "nodes" } ], function(e){
      console.log("cy loaded elements");
    }, function(e){
      console.log("cy laid out elements");
    });

This is equivalent to:

    cy.one("load", function(e){
      console.log("cy loaded elements");
    }).one("layoutstop", function(e){
      console.log("cy laid out elements");
    });

    cy.load([ { data: { id: "n1" }, group: "nodes" } ]);

cy.batchData()
Update several data fields for several elements all at once (in batch).
cy.batchData( , map )

- map Element IDs mapped to data to set.

### Details

This function take a map whose indices are element IDs (e.g. `'n0'`) mapped to objects that are used to update the corresponding data object. If an element already has data with the specified field name, then it is overwritten.

### Examples

    cy.batchData({
      'j': {
          weight: 73 // too much non-fat yoghourt
      },

      'g': {
          weight: 72,
          height: 154 // shoe inserts
      }
    });

cy.collection()
Return a new, empty collection.

### Details

This function is useful for building up collections.

### Examples

Keep a collection of nodes that have been clicked:

    var collection = cy.collection();
    cy.nodes().live("click", function(){
      collection = collection.add(this);
    });

cy.$() et al
Get elements in the graph matching a selector or a filter function.
cy.$( , selector )
Get elements in the graph matching the specified selector.

- selector The selector the elements should match.

cy.elements( , selector )
Get elements in the graph matching the specified selector.

- selector The selector the elements should match.

cy.nodes( , selector )
Get nodes in the graph matching the specified selector.

- selector The selector the nodes should match.

cy.edges( , selector )
Get edges in the graph matching the specified selector.

- selector The selector the edges should match.

cy.filter( , selector )
Get elements in the graph matching the specified selector.

- selector The selector the elements should match.

cy.filter( , function(i, ele) )
Get elements in the graph matching the specified filter function.

- function(i, ele) The filter function that returns true for elements that should be returned.
  - – i The counter used for iteration over the elements in the graph.
  - – ele The current element under consideration for filtering.

### Details

If no elements in the graph match the selector, an empty collection is returned.

The function `cy.$()` acts as an alias to `cy.filter()`: It's just convenient to save you typing. It is analogous to the jQuery `$` alias used to search the document

### Examples

Get nodes with weight greater than 50:

    cy.nodes("[weight>50]");

Get edges with source node `n0`:

    cy.edges("[source='j']");

Get all nodes and edges with weight greater than 50:

    cy.elements("[weight>50]");
    cy.filter("[weight>50]"); // works the same as the above line

Get nodes with weight greater than 50 with a filter function:

    cy.filter(function(i, element){
      if( element.isNode() && element.data("weight") > 50 ){
        return true;
      }
      return false;
    });

## Viewport manipulation

cy.center()
Pan the graph to the centre of a collection.
cy.center()
Centre on all elements in the graph.

cy.center( , eles )
Centre on the specified elements.

- eles The collection to centre upon.

### Details

If an empty collection or no collection is specified, then the graph is centred on all nodes and edges in the graph.

### Examples

Centre the graph on node `j`:

    var j = cy.$("#j");
    cy.center( j );

cy.fit()
Pan and zooms the graph to fit to a collection.
cy.fit()
Fit to all elements in the graph.

cy.fit( [, eles] [, padding] )
Fit to the specified elements.

- eles The collection to fit to.
- padding An amount of padding (in pixels) to have around the graph

### Details

If an empty collection or no collection is specified, then the graph is fit to all nodes and edges in the graph.

### Examples

Fit the graph on nodes `j` and `e`:

    cy.fit( cy.$('#j, #e') );

cy.reset()
Reset the graph to the default zoom level and panning position.
cy.reset()
Resets the zoom and pan.

### Details

This resets the viewport to the origin (0, 0) at zoom level 1.

### Examples

    setTimeout( function(){
        cy.pan({ x: 50, y: -100 });
    }, 1000 );

    setTimeout( function(){
        cy.zoom( 2 );
    }, 2000 );

    setTimeout( function(){
        cy.reset();
    }, 3000 );

cy.pan()
Get or set the panning position of the graph.
cy.pan()
Get the current panning position.

cy.pan( , renderedPosition )
Set the current panning position.

- renderedPosition The rendered position to pan the graph to.

### Details

This function pans the graph viewport origin to the specified rendered pixel position.

### Examples

Pan the graph to (100, 100) rendered pixels.

    cy.pan({
      x: 100,
      y: 100
    });

    console.log( cy.pan() ); // prints { x: 100, y: 100 }

cy.panBy()
Relatively pan the graph by a specified rendered position vector.
cy.panBy( , renderedPosition )

- renderedPosition The rendered position vector to pan the graph by.

### Details

This function shifts the viewport relatively by the specified position in rendered pixels. That is, specifying a shift of 100 to the right means a translation of 100 on-screen pixels to the right.

### Examples

Pan the graph 100 pixels to the right.

    cy.panBy({
      x: 100,
      y: 0
    });

cy.panningEnabled()
Get or set whether panning is enabled.
cy.panningEnabled()
Get whether panning is enabled.

cy.panningEnabled( , bool )
Set whether panning is enabled.

- bool A truthy value enables panning; a falsey value disables it.

cy.zoom()
Get or set the zoom level of the graph.
cy.zoom()
Get the zoom level.

cy.zoom( , level )
Set the zoom level.

- level The zoom level to set.

cy.zoom( , options )
Set the zoom level.

- options The options for zooming.
  - – level The zoom level to set.
  - – position The position about which to zoom.
  - – renderedPosition The rendered position about which to zoom.

### Details

The zoom level must be a positive number. Zoom levels that are not numbers are ignored; zoom levels that are numbers but outside of the range of valid zoom levels are considered to be the closest, valid zoom level.

When zooming about a point via `cy.zoom( options )`, the options are defined as follows.

For zooming about a rendered position (i.e. a position on-screen):

    cy.zoom({
      level: 2.0, // the zoom level
      renderedPosition: { x: 100, y: 100 }
    });

For zooming about a model position:

    cy.zoom({
      level: 2.0, // the zoom level
      position: { x: 0, y: 0 }
    });

For obvious reasons, you can zoom about a position or a rendered position but not both. You should specify only one of `options.position` or `options.renderedPosition`.

### Examples

Zoom in to factor 2

    cy.zoom(2);

Zoom in to the minimum zoom factor

    cy.zoom(0); // 0 is outside of the valid range and
                // its closest valid level is the min

Zoom in to the maximum zoom factor

    cy.zoom(1/0); // infinity is outside of the valid range and
                  // its closest valid level is the max

Zoom about a node

    var pos = cy.nodes("#j").position();
    cy.zoom({
      level: 1.5,
      position: pos
    });

cy.zoomingEnabled()
Get or set whether zooming is enabled.
cy.zoomingEnabled()
Get whether zooming is enabled.

cy.zoomingEnabled( , bool )
Set whether zooming is enabled.

- bool A truthy value enables zooming; a falsey value disables it.

cy.minZoom()
Get or set the minimum zoom level.
cy.minZoom()
Get the minimum zoom level.

cy.minZoom( , zoom )
Set the minimum zoom level.

- zoom The new minimum zoom level to use.

cy.maxZoom()
Get or set the maximum zoom level.
cy.maxZoom()
Get the maximum zoom level.

cy.maxZoom( , zoom )
Set the maximum zoom level.

- zoom The new maximum zoom level to use.

cy.boxSelectionEnabled()
Get or set whether box selection is enabled.
cy.boxSelectionEnabled()
Get whether box selection is enabled.

cy.boxSelectionEnabled( , bool )
Set whether box selection is enabled.

- bool A truthy value enables box selection; a falsey value disables it.

## Events

cy.on()
Bind to events that occur in the graph.
cy.on( , events [, selector] [, data], function(evt) )

- events A space separated list of event names.
- selector A selector to specify elements for which the handler is triggered.
- data A plain object which is passed to the handler in the event object argument.
- function(evt) The handler function that is called when one of the specified events occurs.
  - – evt The event object.

cy.on( , eventsMap [, selector] [, data] )

- eventsMap A map of event names to handler functions.
- selector A selector to specify elements for which the handler is triggered.
- data A plain object which is passed to the handler in the event object argument.

### Examples

Bind to events that bubble up from elements matching the specified `node` selector:

    cy.on('tap', 'node', { foo: 'bar' }, function(evt){
      console.log( evt.data.foo ); // 'bar'

      var node = evt.cyTarget;
      console.log( 'tapped ' + node.id() );
      debugger;
    });

Bind to all tap events that the core receives:

    cy.on('tap', function(event){
      // cyTarget holds a reference to the originator
      // of the event (core or element)
      var evtTarget = event.cyTarget;

      if( evtTarget === cy ){
          console.log('tap on background');
      } else {
        console.log('tap on some element');
      }
    });

cy.one()
Bind to events that occur in the graph, and trigger the handler only once.
cy.one( , events [, data], function(evt) )

- events A space separated list of event names.
- data A plain object which is passed to the handler in the event object argument.
- function(evt) The handler function that is called when one of the specified events occurs.
  - – evt The event object.

cy.one( , eventsMap [, data] )

- eventsMap A map of event names to handler functions.
- data A plain object which is passed to the handler in the event object argument.

### Examples

    cy.one('tap', 'node', function(){
      console.log('tap!');
    });

    cy.$('node').eq(0).trigger('tap'); // tap!
    cy.$('node').eq(1).trigger('tap'); // nothing b/c already tapped

cy.off()
Remove event handlers.
cy.off( , events [, selector] [, handler] )

- events A space separated list of event names.
- selector The same selector used to bind to the events.
- handler A reference to the handler function to remove.

cy.off( , eventsMap [, selector] )

- eventsMap A map of event names to handler functions to remove.
- selector The same selector used to bind to the events.

### Examples

For all handlers:

    cy.on("tap", function(){ /* ... */ });

    // unbind all tap handlers, including the one above
    cy.off("tap");

For a particular handler:

    var handler = function(){
      console.log("called handler");
    };
    cy.on("tap", handler);

    var otherHandler = function(){
      console.log("called other handler");
    };
    cy.on("tap", otherHandler);

    // just unbind handler
    cy.off("tap", handler);

cy.trigger()
Trigger one or more events.
cy.trigger( , events [, extraParams] )

- events A space separated list of event names to trigger.
- extraParams An array of additional parameters to pass to the handler.

### Examples

    cy.bind('tap', function(evt, foo, bar){
      console.log('tap');
    });

    cy.trigger('tap', ['foo', 'bar']);

## Visuals

cy.layout()
Position elements in the graph with a layout.
cy.layout( , options )

- options The layout options.

### Options for included layouts

Several layouts are included with Cytoscape.js by default, and their options are described here with the default values specified. Note that you must set `options.name` to the name of the layout to specify which one you want to run.

The `random` layout:

    options = {
        name: 'random',
        ready: undefined, // callback on layoutready
        stop: undefined, // callback on layoutstop
        fit: true // whether to fit to viewport
    };

    cy.layout( options );

The `preset` layout puts nodes in the positions you specify manually:

    options = {
        name: 'preset',
        fit: true, // whether to fit to viewport
        ready: undefined, // callback on layoutready
        stop: undefined, // callback on layoutstop
        positions: undefined, // map of (node id) => (position obj)
        zoom: undefined, // the zoom level to set (prob want fit = false if set)
        pan: undefined // the pan level to set (prob want fit = false if set)
    };

    cy.layout( options );

The `grid` layout puts nodes in a well-spaced grid:

    options = {
        name: 'grid',
        fit: true, // whether to fit the viewport to the graph
        rows: undefined, // force num of rows in the grid
        columns: undefined, // force num of cols in the grid
        ready: undefined, // callback on layoutready
        stop: undefined // callback on layoutstop
    };

    cy.layout( options );

The `breadthfirst` layout puts nodes in a hierarchy:

    options = {
        fit: true, // whether to fit the viewport to the graph
        ready: undefined, // callback on layoutready
        stop: undefined, // callback on layoutstop
        directed: true, // whether the tree is directed downwards (or edges can point in any direction if false)
        padding: 30, // padding on fit
        circle: false, // put depths in concentric circles if true, put depths top down if false
        roots: undefined, // the roots of the trees
        maximalAdjustments: 0 // how many times to try to position the nodes in a maximal way (i.e. no backtracking)
    };

    cy.layout( options );

The `circle` layout puts nodes in a circle:

    options = {
        name: 'circle',
        fit: true, // whether to fit the viewport to the graph
        ready: undefined, // callback on layoutready
        stop: undefined, // callback on layoutstop
        rStepSize: 10, // the step size for increasing the radius if the nodes don't fit on screen
        padding: 30, // the padding on fit
        startAngle: 3/2 * Math.PI, // the position of the first node
        counterclockwise: false // whether the layout should go counterclockwise (true) or clockwise (false)
    };

    cy.layout( options );

The `arbor` layout uses a force-directed simulation:

    options = {
        liveUpdate: true, // whether to show the layout as it's running
        ready: undefined, // callback on layoutready
        stop: undefined, // callback on layoutstop
        maxSimulationTime: 4000, // max length in ms to run the layout
        fit: true, // reset viewport to fit default simulationBounds
        padding: [ 50, 50, 50, 50 ], // top, right, bottom, left
        simulationBounds: undefined, // [x1, y1, x2, y2]; [0, 0, width, height] by default
        ungrabifyWhileSimulating: true, // so you can't drag nodes during layout

        // forces used by arbor (use arbor default on undefined)
        repulsion: undefined,
        stiffness: undefined,
        friction: undefined,
        gravity: true,
        fps: undefined,
        precision: undefined,

        // static numbers or functions that dynamically return what these
        // values should be for each element
        nodeMass: undefined,
        edgeLength: undefined,

        stepSize: 1, // size of timestep in simulation

        // function that returns true if the system is stable to indicate
        // that the layout can be stopped
        stableEnergy: function( energy ){
            var e = energy;
            return (e.max <= 0.5) || (e.mean <= 0.3);
        }
    };

    cy.layout( options );

Please note that the `liveUpdate` option is expensive, so if you are concerned about running time (e.g. for large graphs), you should set it to `false`.

NB: You must reference the version of `arbor.js` included with Cytoscape.js in the `<head>` of your HTML document:

    <head>
        ...

        <script src="arbor.js"></script>

        ...
    </head>

Arbor does some automatic path finding because it uses web workers, and so it must be included this way. Therefore, you can not combine `arbor.js` with your other JavaScript files — as you probably would as a part of the minification of the scripts in your webapp.

The `null` layout puts all nodes at (0, 0):

    // The null layout has no options.

The `CoSE` (Compound Spring Embedder) layout uses a force-directed simulation to lay out compound graphs.
It was implemented by Gerardo Huck as part of Google Summer of Code 2013.
Mentors: Max Franz, Christian Lopes, Anders Riutta, Ugur Dogrusoz.
Based on the article "A layout algorithm for undirected compound graphs" by Ugur Dogrusoz, Erhan Giral, Ahmet Cetintas, Ali Civril and Emek Demir.

    options = {
        // Number of iterations between consecutive screen positions update (0 -> only updated on the end)
        refresh             : 0,
        // Whether to fit the network view after when done
        fit                 : true,
        // Whether to randomize node positions on the beginning
        randomize           : true,
        // Whether to use the JS console to print debug messages
        debug               : false,

        // Node repulsion (non overlapping) multiplier
        nodeRepulsion       : 10000,
        // Node repulsion (overlapping) multiplier
        nodeOverlap         : 10,
        // Ideal edge (non nested) length
        idealEdgeLength     : 10,
        // Divisor to compute edge forces
        edgeElasticity      : 100,
        // Nesting factor (multiplier) to compute ideal edge length for nested edges
        nestingFactor       : 5,
        // Gravity force (constant)
        gravity             : 250,

        // Maximum number of iterations to perform
        numIter             : 100,
        // Initial temperature (maximum node displacement)
        initialTemp         : 200,
        // Cooling factor (how the temperature is reduced between consecutive iterations)
        coolingFactor       : 0.95,
        // Lower temperature threshold (below this point the layout will end)
        minTemp             : 1
    };

    cy.layout( options );

### Examples

    cy.layout({ name: 'grid' });

cy.style()
Get the entry point to modify the visual style of the graph after initialisation.

### Details

You can use this function to gain access to the visual style after initialisation. This is useful if you need to change the entire stylesheet at runtime, though this is strongly not advised for most developers. It's akin to changing the CSS files you're using on a HTML document on-the-fly.

This example sets an entirely new style to the graph, specifying selectors and style properties:

    cy.style()
      .resetToDefault() // start a fresh default stylesheet

      // and then define new styles
      .selector('node')
          .css('background-color', 'blue')
      .selector('node:selected')
        .css({
          'background-color': 'red'

          // , ...
        })

      // ...

      .update() // update the elements in the graph with the new style

You can also set the style from plain JSON:

    cy.style()
      .fromJson([
        {
          selector: 'node',
          css: {
            'background-color': 'blue'
          }
        },

        {
          selector: 'node:selected',
          css: {
            'background-color': 'red'

            // , ...
          }
        }

        // , ...
      ])

      .update() // update the elements in the graph with the new style

# Collection

A collection contains a set of nodes and edges. Calling a function applies the function to all elements in the collection. When reading values from a collection, `eles.data()` for example, the value of the first element in the collection is returned. This follows the jQuery convention. For example:

    var weight = cy.nodes().data("weight");

    console.log( cy.nodes()[0].data("weight") + ' == ' + weight ); // weight is the first ele's weight

You can insure that you're reading from the element you want by using a selector to narrow down the collection to one element (i.e. `eles.size() === 1`) or the `eles.eq()` function.

## Graph manipulation

eles.remove()
Remove the elements from the graph.

### Details

This function removes the calling elements from the graph. The elements are not deleted — they still exist in memory — but they are no longer in the graph.

NB: A removed element just exists to be added back to its originating core instance or some other core instance. A removed element is not functional, because it is no longer a part of the graph: Nothing really makes sense for it anymore outside of the context of a graph. It merely exists in this limbo state so you can later add it back to some core instance.

### Examples

Remove selected elements:

    cy.$(':selected').remove();

ele.removed()
Get whether the element has been removed from the graph.
eles.restore()
Put removed elements back into the graph.

### Details

This function puts back elements in the graph that have been removed. It will do nothing if the elements are already in the graph.

An element can not be restored if its ID is the same as an element already in the graph. You should specify an alternative ID for the element you want to add in that case.

### Examples

    // remove selected elements
    var eles = cy.$(':selected').remove();

    // ... then some time later put them back
    eles.restore();

## Data

eles.data()
Read and write developer-defined data associated with the elements.
ele.data()
Get all data for the element.

ele.data( , name )
Get a particular data field for the element.

- name The name of the field to get.

ele.data( , name, value )
Set a particular data field for the element.

- name The name of the field to set.
- value The value to set for the field.

ele.data( , obj )
Update multiple data fields at once via an object.

- obj The object containing name-value pairs to update data fields.

### Details

The following fields are immutable:

- `id` : The `id` field is used to uniquely identify an element in the graph.
- `source` & `target` : These fields define an edge's relationship to nodes, and this relationship can not be changed after creation.
- `parent` : The `parent` field defines the parent (compound) node.

### Examples

    var j = cy.$('#j');

    // set the weight field in data
    j.data('weight', 60);

    // set several fields at once
    j.data({
      name: 'Jerry Jerry Dingleberry',
      height: 176
    });

    var weight = j.data('weight');

eles.removeData()
Remove developer-defined data associated with the elements.
eles.removeData()
Removes all mutable data fields for the elements.

eles.removeData( , names )
Removes the specified mutable data fields for the elements.

- names A space-separated list of fields to delete.

### Details

The following data fields are immutable, and so they can not be removed:

- `id` : The `id` field is used to uniquely identify an element in the graph.
- `source` & `target` : These fields define an edge's relationship to nodes, and this relationship can not be changed after creation.
- `parent` : The `parent` field defines the parent (compound) node.

ele.id()
A shortcut to get the ID of an element.
ele.json()
Get the element's plain JavaScript object representation.

### Details

This function returns the plain JSON representation of the element, the same format which is used at initialisation, in `cy.load()`, in `cy.add()` etc.

ele.group()
Get the group string that defines the type of the element.

### Details

The group strings are `"nodes"` for nodes and `"edges"` for edges. In general, you should be using `ele.isEdge()` and `ele.isNode()` instead of `ele.group()`.

ele.isNode()
Get whether the element is a node.
ele.isEdge()
Get whether the element is an edge.

## Metadata

node.degree() et al
node.degree()
Get the degree of a node.

node.indegree()
Get the indegree of a node.

node.outdegree()
Get the outdegree of a node.

nodes.totalDegree()
Get the total degree of a collection of nodes.

nodes.minDegree()
Get the minimum degree of the nodes in the collection.

nodes.maxDegree()
Get the maximum degree of the nodes in the collection.

nodes.minIndegree()
Get the minimum indegree of the nodes in the collection.

nodes.maxIndegree()
Get the maximum indegree of the nodes in the collection.

nodes.minOutdegree()
Get the minimum outdegree of the nodes in the collection.

nodes.maxOutdegree()
Get the maximum outdegree of the nodes in the collection.

### Details

Degree : For a node, the degree is the number of edge connections it has. Each time a node is referenced as `source` or `target` of an edge in the graph, that counts as an edge connection.

Indegree : For a node, the indegree is the number of incoming edge connections it has. Each time a node is referred to as `target` of an edge in the graph, that counts as an incoming edge connection.

Outdegree : For a node, the outdegree is the number of outgoing edge connections it has. Each time a node is referred to as `source` of an edge in the graph, that counts as an outgoing edge connection.

Total degree : For a set of nodes, the the total degree is the total number of edge connections to nodes in the set.

## Position & dimensions

node.position()
Get or set the position of a node.
node.position()
Get the entire position object.

node.position( , dimension )
Get the value of a specified position dimension.

- dimension The position dimension to get.

node.position( , dimension, value )
Set the value of a specified position dimension.

- dimension The position dimension to set.
- value The value to set to the dimension.

node.position( , pos )
Set the position using name-value pairs in the specified object.

- pos An object specifying name-value pairs representing dimensions to set.

### Details

A position has two fields, `x` and `y`, that can take on numerical values. Non-numerical values are ignored.

### Examples

    // get x for j
    var x = cy.$('#j').position('x');

    // get the whole position for e
    var pos = cy.$('#e').position();

    // set y for j
    cy.$('#j').position('y', 100);

    // set multiple
    cy.$('#e').position({
      x: 123,
      y: 200
    });

nodes.positions()
Set the positions of several nodes with a function.
nodes.positions( , fn(i, ele) )

- fn(i, ele) A callback function that returns the position to set for each element.
  - – i The index of the element when iterating over the elements in the collection.
  - – ele The element being iterated over for which the function should return a position to set.

node.renderedPosition()
Get or set the rendered position of a node.
node.renderedPosition()
Get the entire rendered position object.

node.renderedPosition( , dimension )
Get the value of a specified rendered posisition dimension.

- dimension The position dimension to get.

node.renderedPosition( , dimension, value )
Set the value of a specified rendered posisition dimension.

- dimension The position dimension to set.
- value The value to set to the dimension.

node.renderedPosition( , pos )
Set the rendered position using name-value pairs in the specified object.

- pos An object specifying name-value pairs representing dimensions to set.

ele.width() et al
Get the width of the element.
ele.width()
Get the width of the element.

ele.outerWidth()
Get the outer width of the element (width & border).

ele.renderedWidth()
Get the width of the element in rendered dimensions.

ele.renderedOuterWidth()
Get the outer width of the element (width & border) in rendered dimensions.

ele.height() et al
Get the height of the element.
ele.height()
Get the height of the element.

ele.outerHeight()
Get the outer height of the element (height & border).

ele.renderedHeight()
Get the height of the element in rendered dimensions.

ele.renderedOuterHeight()
Get the outer height of the element (height & border) in rendered dimensions.

node.grabbed()
Get whether a node is currently grabbed, meaning the user has hold of the node.
node.grabbable()
Get whether the user can grab a node.
nodes.grabify()
Allow the user to grab the nodes.
nodes.ungrabify()
Disallow the user to grab the nodes.
node.locked()
Get whether a node is locked, meaning that its position can not be changed.
nodes.lock()
Lock the nodes such that their positions can not be changed.
nodes.unlock()
Unlock the nodes such that their positions can be changed.
ele.active()
Gets whether the element is active (e.g. on user tap, grab, etc).

## Selection

ele.selected()
Get whether the element is selected.
eles.select()
Make the elements selected (NB other elements outside the collection are not affected).
eles.unselect()
Make the elements not selected (NB other elements outside the collection are not affected).
ele.selectable()
Get whether the element's selection state is mutable.
eles.selectify()
Make the selection states of the elements mutable.
eles.unselectify()
Make the selection states of the elements immutable.

## Events

eles.on()
Bind to events that occur on the elements.
eles.on( , events [, data], function(evt) )

- events A space separated list of event names.
- data A plain object which is passed to the handler in the event object argument.
- function(evt) The handler function that is called when one of the specified events occurs.
  - – evt The event object.

eles.on( , eventsMap [, selector] [, data] )

- eventsMap A map of event names to handler functions.
- selector A selector to specify elements for which the handler is triggered.
- data A plain object which is passed to the handler in the event object argument.

### Defails

In the handler function, `this` references the originally bound object, and `evt.cyTarget` references the target of the event.

### Examples

    cy.on('tap', function(evt){
      console.log( 'tap ' + evt.cyTarget.id() );
    });

eles.one()
Bind a callback function that is triggered once per event per element.
eles.one( , events [, data], function(evt) )

- events A space separated list of event names.
- data A plain object which is passed to the handler in the event object argument.
- function(evt) The handler function that is called when one of the specified events occurs.
  - – evt The event object.

eles.one( , eventsMap [, data] )

- eventsMap A map of event names to handler functions.
- data A plain object which is passed to the handler in the event object argument.

### Details

For each event specified to this function, the handler function is triggered once per element. This is useful for one-off events that occur on each element once.

### Examples

    cy.$('node').one('tap', function(e){
      var ele = e.cyTarget;
      console.log('tapped ' + ele.id());
    });

eles.once()
Bind a callback function that is triggered once per event per collection.
eles.once( , events [, data], function(evt) )

- events A space separated list of event names.
- data A plain object which is passed to the handler in the event object argument.
- function(evt) The handler function that is called when one of the specified events occurs.
  - – evt The event object.

eles.once( , eventsMap [, data] )

- eventsMap A map of event names to handler functions.
- data A plain object which is passed to the handler in the event object argument.

### Details

For each event specified to this function, the handler function is triggered once. This is useful for one-off events that occur on just one element in the collection.

### Examples

    cy.$('node').once('click', function(e){
      var ele = e.cyTarget;
      console.log('clicked ' + ele.id());
    });

eles.off()
Unbind one or more callback functions on the elements.
eles.off( , events [, handler] )

- events A space separated list of event names.
- handler A reference to the handler function to remove.

eles.off( , eventsMap [, selector] )

- eventsMap A map of event names to handler functions to remove.
- selector The same selector used to bind to the events.

### Examples

    var j = cy.$('#j');
    var handler = function(){ console.log('tap') };

    // bind
    j.on('tap', handler);

    // bind some other handler
    j.on('tap', function(){
      console.log('some other handler');
    });

    j.trigger('tap'); // 'tap' & 'some other handler'

    // unbind the renferenced handler
    j.off('tap', handler);

    j.trigger('tap'); // some other handler

    // unbind all tap handlers (including unnamed handler)
    j.off('tap');

eles.trigger()
Trigger events on the elements.
eles.trigger( , events [, extraParams] )

- events A space separated list of event names to trigger.
- extraParams An array of additional parameters to pass to the handler.

### Examples

    var j = cy.$('#j');

    j.on('tap', function(){
      console.log('tap!!');
    });

    j.trigger('tap'); // tap!!

## Style

eles.css()
Get the style of the element, or override the style of the elements.
ele.css()
Get a name-value pair object containing visual style properties and their values for the element.

ele.css( , name )
Get a particular style property value.

- name The name of the visual style property to get.

eles.css( , name, value )
Set the specified visual style property for the elements.

- name The name of the property to set.
- value The value to set to the visual style property.

eles.css( , props )
Set several visual style properties at once for the elements.

- props An object with name-value pairs representing properties to set on the elements.

### Details

You should use this function very sparingly, because it overrides the style of an element, despite the state and classes that it has. In general, it's much better to specify a better stylesheet at initialisation that reflects your application state rather than programmatically modifying style.

Only defined visual style properties are supported.

If you would like to remove a particular overridden style property, set `null` to it.

eles.removeCss()
Removes all overridden style of the elements.
ele.renderedCss()
Get the style of the element in rendered dimensions.
ele.renderedCss()
Get a name-value pair object containing rendered visual style properties and their values for the element.

ele.renderedCss( , name )
Get a particular rendered style property value.

- name The name of the visual style property to get.

eles.show()
Override the style of the elements such that they are visible.
eles.hide()
Override the style of the elements such that they are hidden.
ele.visible() et al
Get whether the element is visible.
ele.visible()
Get whether the element is visible.

ele.hidden()
Get whether the element is hidden.

eles.addClass()
Add classes to elements.
eles.addClass( , classes )

- classes A space-separated list of class names to add to the elements.

eles.removeClass()
Remove classes from elements.
eles.removeClass( , classes )

- classes A space-separated list of class names to remove from the elements.

eles.toggleClass()
Toggle whether the elements have the specified classes.
eles.toggleClass( , classes [, toggle] )

- classes A space-separated list of class names to toggle on the elements.
- toggle Instead of automatically toggling, adds the classes on truthy values or removes them on falsey values.

ele.hasClass()
Get whether an element has a particular class.
ele.hasClass( , className )

- className The name of the class to test for.

## Animation

ele.animated()
Get whether the element is currently being animated.
eles.animate()
Animate the elements.
eles.animate( , props, options )

- props An object containing the properties to animate.
  - – position A position to which the elements will be animated.
  - – css An object containing name-value pairs of style properties to animate.
- options An object containing animation options.
  - – duration The duration of the animation in milliseconds.
  - – queue A boolean indicating whether to queue the animation.
  - – complete A function to call when the animation is done.
  - – step A function to call each time the animation steps.

### Examples

    cy.nodes().animate({
      position: { x: 100, y: 100 },
      css: { backgroundColor: 'red' }
    }, {
      duration: 1000
    });

eles.delay()
Add a delay between animations for the elements.
eles.delay( , duration, complete )

- duration How long the delay should be in milliseconds.
- complete A function to call when the delay is complete.

eles.stop()
Stop all animations that are currently running.
eles.stop( , clearQueue, jumpToEnd )

- clearQueue A boolean, indicating whether the queue of animations should be emptied.
- jumpToEnd A boolean, indicating whether the currently-running animations should jump to their ends rather than just stopping midway.

eles.clearQueue()
Remove all queued animations for the elements.

## Comparison

eles.same()
Determine whether this collection contains exactly the same elements as another collection.
eles.same( , eles )

- eles The other elements to compare to.

eles.anySame()
Determine whether this collection contains any of the same elements as another collection.
eles.anySame( , eles )

- eles The other elements to compare to.

eles.allAreNeighbors()
Determine whether all elements in the specified collection are in the neighbourhood of the calling collection.
eles.allAreNeighbors( , eles )

- eles The other elements to compare to.

eles.is()
Determine whether any element in this collection matches a selector.
eles.is( , selector )

- selector The selector to match against.

eles.allAre()
Determine whether all elements in the collection match a selector.
eles.allAre( , selector )

- selector The selector to match against.

## Iteration

eles.size()
Get the number of elements in the collection.

### Details

Note that as a non-functional alternative, you may read `eles.length` instead of `eles.size()`. The two are interchangeable.

eles.empty() et al
Get whether the collection is empty, meaning it has no elements.
eles.empty()
Get whether the collection is empty.

eles.nonempty()
Get whether the collection is non-empty.

eles.each()
Iterate over the elements in the collection.
eles.each( , function(i, ele) )

- function(i, ele) The function executed each iteration.
  - – i The index of the element in the collection.
  - – ele The element at the current index.

### Examples

    cy.elements().each(function(i, ele){
      console.log( ele.id() + ' is ' + ( ele.selected() ? 'selected' : 'not selected' ) );
    });

eles.eq()
Get an element at a particular index in the collection.
eles.eq( , index )

- index The index of the element to get.

eles.slice()
Get a subset of the elements in the collection based on specified indices.
eles.slice( , start [, end] )

- start An integer that specifies where to start the selection. The first element has an index of 0. Use negative numbers to select from the end of an array.
- end An integer that specifies where to end the selection. If omitted, all elements from the start position and to the end of the array will be selected. Use negative numbers to select from the end of an array.

## Traversing

eles.neighborhood() et al
Get the neighbourhood of the elements.
eles.neighborhood( [, selector] )
Get the open neighbourhood of the elements.

- selector An optional selector that is used to filter the resultant collection.

eles.openNeighborhood( [, selector] )
Get the open neighbourhood of the elements.

- selector An optional selector that is used to filter the resultant collection.

eles.closedNeighborhood( [, selector] )
Get the closed neighbourhood of the elements.

- selector An optional selector that is used to filter the resultant collection.

### Details

The neighbourhood returned by this function is a bit different than the traditional definition of a "neighbourhood": This returned neighbourhood includes the edges connecting the collection to the neighbourhood. This gives you more flexibility.

An open neighbourhood is one that does not include the original set of elements. If unspecified, a neighbourhood is open by default.

A closed neighbourhood is one that does include the original set of elements.

nodes.edgesWith()
Get the edges connecting the collection to another collection. Direction of the edges does not matter.
nodes.edgesWith( , eles )

- eles The other collection.

nodes.edgesWith( , selector )

- selector The other collection, specified as a selector which is matched against all elements in the graph.

nodes.edgesTo()
Get the edges coming from the collection (i.e. the source) going to another collection (i.e. the target).
nodes.edgesTo( , eles )

- eles The other collection.

nodes.edgesTo( , selector )

- selector The other collection, specified as a selector which is matched against all elements in the graph.

edges.connectedNodes()
Get the nodes connected to the edges in the collection.
edges.connectedNodes( [, selector] )

- selector An optional selector that is used to filter the resultant collection.

edges.source()
Get source nodes connected to the edges in the collection.
edges.source( [, selector] )

- selector An optional selector that is used to filter the resultant collection.

edges.target()
Get target nodes connected to the edges in the collection.
edges.target( [, selector] )

- selector An optional selector that is used to filter the resultant collection.

edges.parallelEdges()
Get edges parallel to those in the collection.
edges.parallelEdges( [, selector] )

- selector An optional selector that is used to filter the resultant collection.

### Details

Two edges are said to be parallel if they connect the same two nodes. That is,

- `edge1.source() === edge2.source() && edge1.target() === edge2.target()` or
- `edge1.source() === edge2.target() && edge1.target() === edge2.source()`.

edges.codirectedEdges()
Get edges codirected to those in the collection.
edges.codirectedEdges( [, selector] )

- selector An optional selector that is used to filter the resultant collection.

### Details

Two edges are said to be codirected if they connect the same two nodes in the same direction. That is, `edge1.source() === edge2.source() && edge1.target() === edge2.target()`.

eles.breadthFirstSearch()
Perform a breadth-first search, with this collection as the root nodes of the search.
eles.breadthFirstSearch( [, function(i, depth)] [, directed] )

- function(i, depth) A handler function that is called when a node is visited in the search.
  - – i The index indicating this node is the ith visited node.
  - – depth How many edge hops away this node is from the root nodes.
- directed A boolean indicating whether the search should only go along edges from source to target (default true).

### Details

This function has a shorter alias, `eles.bfs()`.

### Examples

    cy.$('#j').bfs(function(i, depth){
      console.log('visit ' + this.id());
    }, false);

## Building & filtering

eles.add()
Get a new collection, resulting from adding the collection with another one
eles.add( , eles )

- eles The elements to add.

eles.not()
Get a new collection, resulting from the collection without some specified elements.
eles.not( , eles )

- eles The elements that will not be in the resultant collection.

eles.not( , selector )

- selector Elements from the calling collection matching this selector will not be in the resultant collection.

eles.intersect()
Get the elements in both this collection and another specified collection.
eles.intersect( , eles )

- eles The elements to intersect with.

eles.filter() et al
Get a new collection containing elements that are accepted by the specified filter.
eles.filter( , selector )
Get the elements that match the specified selector.

- selector The selector to match against.

eles.filter( , function(i, ele) )
Get the elements that match the specified filter function.

- function(i, ele) The filter function that returns true for elements to include.
  - – i The index of the current element being considered.
  - – ele The element being considered.

eles.nodes( , selector )
Get the nodes that match the specified selector.

- selector The selector to match against.

eles.edges( , selector )
Get the edges that match the specified selector.

- selector The selector to match against.

# Architecture

Cytoscape.js uses an event-driven model with a core API. The core has several extensions, each of which is notified of events by the core, as needed. Extensions modify the elements in the graph and notify the core of any changes.

The client application accesses Cytoscape.js solely through the core. Clients do not access extensions directly, apart from the case where a client wishes to write his own custom extension.

The following diagram summarises the extensions of Cytoscape.js, which are discussed in further detail later in this documentation.

# Extensions

## API

The extensions API is very simple, following this format:

    cytoscape( type, name, extension );

The value of `type` can take on the following values:

- `core` : The extension adds a core function.
- `collection` : The extension adds a collection function.
- `layout` : The extension registers a layout prototype.
- `renderer` : The extension registers a renderer prototype.

The `name` argument indicates the name of the extension, which should be a single word in lower case.

## Functions

Functions should be chainable, unless they need to return some other value. To make a function chainable, make sure to `return this;` at the end of your function.

Here is an example collection function:

    cytoscape('collection', 'forEach', function( fn ){
      for( var i = 0; i < this.length; i++ ){
        fn.apply( this[i], [ i, this[i] ] );
      }

      return this; // chainability
    });

    cy.elements().forEach(function(){
      console.log( 'forEach ' + this.id() );
    });

## Layouts

A layout modifies the positions of nodes in the graph. A layout has number of options, which are specific to the particular layout.

Layouts may be blocking if they are fast — meaning you can execute your code to run after the layout on the line following the layout call. Layouts may also be continuous, in which case, callback functions are provided to know when the layout finishes.

A layout has two events that must be triggereed on the core, including `layoutready` and `layoutstop`:

- `layoutready` : This is triggered on the core (via `cy.trigger('layoutready')`) when the layout has set the positions on every node at least once. This lets the core know that the nodes now have valid positions and can be rendered. It is important to trigger `layoutready` on continuous layouts so that the nodes are shown moving. For blocking (non-continous) layouts, `layoutready` can just be triggered after the layout is done but before `layoutstop`.

- `layoutstop` : This is triggered on the core (via `cy.trigger('layoutstop')`) when the layout has finished. It should be triggered after `layoutready`. The layout should not change node positions after triggering `layoutstop`.

For an example layout, please refer to the null layout source code. The layout just sets each node to position (0, 0), and it is well documented. The Arbor layout is a good example of a continuous layout.

## Renderers

For an example renderer, please refer to the canvas renderer.

The API of the renderer follows the actor model, and so it has a single main entry point, the `notify()` function. The core uses the `notify()` function to send event objects to the renderer. The format of the event object is as follows:

- `event.type` : A string containing the name of the event that has occured.
- `event.collection` : A collection of elements associated with the event.

If you're interested in writing a custom renderer for Cytoscape.js, please file an issue for more help if needed.