### Hierarchy

- Model
  - GraphLinksModel
  - TreeModel

Models hold the essential data of a diagram, describing the basic entities and their properties and relationships without specifying the appearance and behavior of the Nodes and Links and Groups that represent them visually. Models tend to hold only relatively simple data, making them easy to persist by serialization as JSON or XML formatted text.

Models hold simple data objects, not Parts such as Nodes or Links. Node data is normally represented in a Diagram by instances of Node, but they could be represented by simple Parts or by Groups. A Diagram constructs Parts for its Diagram.model's data by copying templates. Templates are Panels of GraphObjects that get some property values from the model data, accessible via the Panel.data property, using data Binding. See Using Models and Data Binding for an introduction.

This Model class only supports holding an array of node data and interpreting properties on that data to be able to refer to them using unique key values. To support simple tree-structured graphs, use a TreeModel, which inherits from this class. To support links and grouping, use a GraphLinksModel.

Each node data object is assumed to have a unique key value. The nodeKeyProperty property names the property on the node data whose value is the unique key for that node data object. The default value for this property is "key". You should not have a TwoWay data binding on the node key property, because that might cause the property value to be set to a duplicate key value.

The key values must be either strings or numbers or undefined. If the key is undefined, or if there are duplicate key values, the model will automatically try to assign a new unique key value. Caution: if your keys are numbers, do not try to use string representations of those numbers as keys. Conversely, if your keys are strings that happen to have number syntax, do not try to use those number values. Sometimes JavaScript will automatically convert from string to number or vice-versa, but sometimes it won't.

For example, one can define a graph consisting of just two nodes:

     model.nodeDataArray = [
       { key: "Alpha" },
       { key: "Beta" }
     ];

This model cannot detect the modification of the nodeDataArray array or the modification of any node data object. If you want to add or remove node data from the nodeDataArray, call the addNodeData or removeNodeData methods.

If you want to modify a node data object, it depends on whether the property you want to change is a structural property that the model needs to know about, or whether it is a property that is only used for data binding or other application-specific purposes.

For the former case, call the appropriate method, such as setKeyForNodeData, setCategoryForNodeData, GraphLinksModel.setToKeyForLinkData, or GraphLinksModel.setGroupKeyForNodeData. These methods have names that start with "set", "add", "insert", or "remove".

For the latter case, when setting an application-specific property, typically for data binding, and to support undo/redo, call setDataProperty.

The copyNodeData method can be called to make a shallow copy of a node data object. However, if some of those property values are Arrays that want not to be shared but to be copied, you can set copiesArrays to true. This is typically very useful when dealing with data bound item arrays. Furthermore if the items in those copied Arrays are in fact Objects that need to be copied, you can also set copiesArrayObjects to true, causing a copied Array to refer to newly shallow-copied objects of the original array.

Each model raises ChangedEvents that you can follow by registering a listener via addChangedListener. Read more at the Introduction page: Changed Events.

Each model comes with its own UndoManager that is initially not enabled. You will need to set UndoManager.isEnabled to true in order for the UndoManager to record model changes and for your users to perform undo and redo.

You can temporarily turn off the recording of changes by setting skipsUndoManager to true. A number of places within the system do that routinely in order to avoid recording temporary changes, so be sure to remember the original value beforehand and restore it afterwards. Note that in a ChangedEvent listener you may want to ignore events that happen when skipsUndoManager is true.

One normally saves a diagram by just saving its model. If you can use JSON-formatted text, this is easy to do -- just call toJson to get the string representation of the model, and save that string. Load the diagram by replacing the Diagram.model with one created by calling the static function Model.fromJson:

      myDiagram.model = go.Model.fromJson(loadedString);

Note that JSON and other textual data formats cannot faithfully store all JavaScript functions. toJson and Model.fromJson do not try to save and load functional property values. You should arrange that all such functions, including event handlers, are established by your app. toJson and Model.fromJson also cannot handle circular references; any sharing of references will be lost too. They also skip properties that are not enumerable, those whose names start with an underscore, and those whose values are undefined.

Note that models also do not store the templates used by diagrams, nor any transient or temporary parts such as Adornments, nor any tools, nor any UndoManager state, nor any event listeners. These objects and all other properties of diagrams must be established by your app.

You can add any number of properties to the modelData object, which is serialized and deserialized into JSON just like any other model data for nodes or links. However modelData is associated with the model as a whole and does not depend on the existence of any node data or link data.

It is also easy to save the changes that were recorded in the most recent transaction. Call toIncrementalJson to generate a JSON-format string that holds the current state of modified data plus the keys of inserted or removed data. That method requires as an argument a ChangedEvent that represents a transaction that completed or an undo or a redo that just finished.

It is also possible to use such "incremental" JSON to modify an existing model. Call applyIncrementalJson, giving it a string generated by toIncrementalJson, to modify this model by making all of the changes recorded in the JSON text. Note how this method is a regular instance method, whereas Model.fromJson is a static function.

## Index

### Constructors

- constructor

### Properties

- copiesArrayObjects
- copiesArrays
- copiesKey
- copyNodeDataFunction
- dataFormat
- isReadOnly
- makeUniqueKeyFunction
- modelData
- name
- nodeCategoryProperty
- nodeDataArray
- nodeKeyProperty
- skipsUndoManager
- undoManager

### Methods

- addArrayItem
- addChangedListener
- addNodeData
- addNodeDataCollection
- applyIncrementalJson
- assignAllDataProperties
- clear
- cloneDeep
- cloneProtected
- commit
- commitTransaction
- containsNodeData
- copy
- copyNodeData
- findNodeDataForKey
- getCategoryForNodeData
- getKeyForNodeData
- insertArrayItem
- makeNodeDataKeyUnique
- mergeNodeDataArray
- raiseChangedEvent
- raiseDataChanged
- removeArrayItem
- removeChangedListener
- removeNodeData
- removeNodeDataCollection
- rollbackTransaction
- set
- setCategoryForNodeData
- setDataProperty
- setKeyForNodeData
- startTransaction
- toIncrementalData
- toIncrementalJson
- toJson
- updateTargetBindings
- fromJson

## Constructors

### constructor

- new Model(nodedataarray?: ObjectData[], init?: Partial<Model>): Model
- new Model(init?: Partial<Model>): Model

- You probably don't want to call this constructor, because this class does not support links (relationships between nodes) or groups (nodes and links and subgraphs as nodes): instead, create instances of a subclass such as GraphLinksModel or TreeModel.

  #### Parameters

  - ##### Optional nodedataarray: ObjectData[]

    an optional Array containing JavaScript objects to be represented by Parts.

  - ##### Optional init: Partial<Model>

    Optional initialization properties.

  #### Returns Model

- You probably don't want to call this constructor, because this class does not support links (relationships between nodes) or groups (nodes and links and subgraphs as nodes): instead, create instances of a subclass such as GraphLinksModel or TreeModel.

  #### Parameters

  - ##### Optional init: Partial<Model>

    Optional initialization properties.

  #### Returns Model

## Properties

### copiesArrayObjects: boolean

- Gets or sets whether the default behavior for copyNodeData or GraphLinksModel.copyLinkData when copying Arrays also copies array items that are Objects. This only covers copying Objects that are items in Arrays that are copied when copiesArrays is true. Copying an Object when this property is true also recursively copies any Arrays that are property values. It also assumes that the object's constructor can be called with no arguments.

  The default value is false. This property does not affect any behavior when the value of copyNodeDataFunction or GraphLinksModel.copyLinkDataFunction has been set to a function. This property has no effect unless copiesArrays is true.

  Caution: if you want a copied data object to share some references but not others, you will need to provide your own copying function as copyNodeDataFunction rather than setting this property and copiesArrays to true.

  Warning: there should not be any cyclical references within the model data.

  see

    copiesArrays, copyNodeDataFunction

  since

    1.5

### copiesArrays: boolean

- Gets or sets whether the default behavior for copyNodeData or GraphLinksModel.copyLinkData makes copies of property values that are Arrays. This only copies Arrays that are top-level property values in data objects, not for Arrays that are in nested objects. Copying Arrays will also copy any array items that are Objects when copiesArrayObjects is true.

  The default value is false. It is commonplace to set copiesArrayObjects to true when setting this property to true. This property does not affect any behavior when the value of copyNodeDataFunction or GraphLinksModel.copyLinkDataFunction has been set to a function.

  Caution: if you want a copied data object to share some Arrays but not others, you will need to provide your own copying function as copyNodeDataFunction rather than setting this property to true.

  Warning: there should not be any cyclical references within the model data.

  see

    copiesArrayObjects, copyNodeDataFunction

  since

    1.5

### copiesKey: boolean

- Gets or sets whether the default behavior for copyNodeData or GraphLinksModel.copyLinkData when copying properties of a data object also copies the key property value. Set this to false in order to force a unique key generation for data copied from another Diagram, such as a Palette.

  The default value is true. This property does not affect any behavior when the value of copyNodeDataFunction has been set to a function.

  see

    copiesArrays, copyNodeDataFunction

  since

    2.0

### copyNodeDataFunction: (data: ObjectData, model: Model) => ObjectData

- Gets or sets a function that makes a copy of a node data object.

  You may need to set this property in order to ensure that a copied Node is bound to data that does not share certain data structures between the original node data and the copied node data. This property value may be null in order to cause copyNodeData to make a shallow copy of a JavaScript Object. The default value is null.

  The first argument to the function will be a node data object (potentially a Part's Panel.data). The second argument to the function will be this Model itself.

  It is common to implement a copying function when the node data has an Array of data and that Array needs to be copied rather than shared. Often the objects that are in the Array also need to be copied.

### dataFormat: string

- Gets or sets the name of the format of the diagram data. The default value is the empty string. The value must not be null. Use different values to prevent parts from one model to be copy/pasted or drag-and-dropped into another diagram/model.

### isReadOnly: boolean

- Gets or sets whether this model may be modified, such as adding nodes. By default this value is false. Setting the nodeDataArray to something that is not a true Array of Objects will cause this to be set to true.

  Model methods and property setters do not heed this property. It is up to code that uses a model to check this property when it might want to prevent changes to the model.

### makeUniqueKeyFunction: (model: Model, data: ObjectData) => Key

- Gets or sets a function that returns a unique id number or string for a node data object. This function is called by makeNodeDataKeyUnique when a node data object is added to the model, either as part of a new nodeDataArray or by a call to addNodeData, to make sure the value of getKeyForNodeData is unique within the model.

  The value may be null in order to cause makeNodeDataKeyUnique behave in the standard manner. (The default value is null.) You may want to supply a function here in order to make sure all of the automatically generated keys are in a particular format. Setting this property after setting nodeDataArray has no real effect until there is a call to addNodeData.

  If you want to ensure that this function is called when copying data that already has a key, set copiesKey to false. This is typically useful when copying a node from a Palette, where the key it has in the Palette's Model happens to be unique within the target Diagram's Model. Unless you set copiesKey to false, the original key value will be copied and retained if it is already unique within the target model.

  If a node data object is already in the model and you want to change its key value, call setKeyForNodeData with a new and unique key.

### modelData: ObjectData

- Gets a JavaScript Object that can hold programmer-defined property values for the model as a whole, rather than just for one node or one link.

  By default this an object with no properties. Any properties that you add to this object will be written out by toJson and will be restored by Model.fromJson, if the following conditions are true:

  - the property is enumerable and its name does not start with an underscore ('_')
  - the property value is not undefined and is not a function
  - the model knows how to convert the property value to JSON format
  - property values that are Objects or Arrays form a tree structure -- no shared or cyclical references

  Most object classes cannot be serialized into JSON without special knowledge and processing at both ends. The toJson and Model.fromJson methods automatically do such processing for numbers that are NaN and for objects that are of class Point, Size, Rect, Margin, Spot, Brush (but not for brush patterns), and for Geometry.

  At the current time one cannot have a Diagram as a binding target. Calling setDataProperty will work to change a property value, but there are no target bindings in any Diagrams to be updated. Because the binding mechanism is unavailable for this object, we recommend that when you want to save a model that you explicitly set properties on this object just before calling toJson. When loading a model, call Model.fromJson and explicitly get the properties that you want to set on a Diagram.

### name: string

- Gets or sets the name of this model. The initial name is an empty string. The value must not be null.

### nodeCategoryProperty: string | ((a: ObjectData, b?: string) => string)

- Gets or sets the name of the node data property that returns a string naming that data's category. The value may also be a function taking two arguments, where the first argument will be a node data object. If the second argument is not supplied, the function should return the category name; if the second argument is supplied, the function should modify the node data object so that it has that new category name. The default value is the string 'category', meaning that it expects the data to have a property named 'category' if it cares to name a category. This is used by the diagram to distinguish between different kinds of nodes. The name must not be null. If the value is an empty string, getCategoryForNodeData will return an empty string for all node data objects.

  If you want to set this property you must do so before using the model, and especially before you assign Diagram.model. Note that functions cannot be serialized into JSON-formatted text, so if you are using toJson and Model.fromJson, and if you want this property to be a function, you will need to assign this property to your desired function immediately after creating the model, including when it is created by Model.fromJson.

  see

    getCategoryForNodeData, setCategoryForNodeData

### nodeDataArray: ObjectData[]

- Gets or sets the array of node data objects that correspond to Nodes, Groups, or non-Link Parts in the Diagram. The initial value is an empty Array.

  For each Object in the Array, getKeyForNodeData should return a number or string uniquely identifying the node data within the model. If it returns undefined, this calls makeNodeDataKeyUnique, to make sure the node data has a unique key. These key values may be used by other objects to refer to that particular node data object. If more than one node data object has the same key, there may be some confusion about which object to reference.

  If you want to use a custom data property for holding the unique key value on a node data object, you should set nodeKeyProperty before you set this `nodeDataArray` property.

  Adding or removing data from this Array will not notify this model or the diagram that there are any new nodes or that any nodes have been deleted. Instead you should call addNodeData or removeNodeData.

### nodeKeyProperty: string | ((a: ObjectData, b?: Key) => Key)

- Gets or sets the name of the data property that returns a unique id number or string for each node data object. The value may also be a function taking two arguments, where the first argument will be a node data object. If the second argument is not supplied, the function should return the unique key value; if the second argument is supplied, the function should modify the node data object so that it has that new value as its unique key value. The default value is the name 'key', meaning that it expects the data to have a property named 'key' if it has a key value. The name must not be null or the empty string. You must set this property before assigning the nodeDataArray.

  If you want to set this property you must do so before using the model, and especially before you assign Diagram.model. Note that functions cannot be serialized into JSON-formatted text, so if you are using toJson and Model.fromJson, and if you want this property to be a function, you will need to assign this property to your desired function immediately after creating the model, including when it is created by Model.fromJson.

  see

    getKeyForNodeData

### skipsUndoManager: boolean

- Gets or sets whether ChangedEvents are not recorded by the UndoManager. The initial and normal value is false. WARNING: while this property is true do not perform any changes that cause any previous transactions to become impossible to undo.

  When this property is true, changing the Model or any data object does not call UndoManager.handleChanged. Even when this property is true, transactions (such as calls to startTransaction) and undo/redo (such as calls to CommandHandler.undo) are still delegated to the undoManager.

  You should set this to true only temporarily, and you should remember its previous value before setting this to true. When finishing the period for which you want the UndoManager to be disabled, do not blindly set this property to false. You should set this back to the value it had before you set it to true. For more permanent disabling of the UndoManager, set UndoManager.isEnabled to false.

  This property is also set when setting Diagram.skipsUndoManager. Setting this property does not raise a ChangedEvent.

### undoManager: UndoManager

- Gets or sets the UndoManager for this Model.

  The default UndoManager has its UndoManager.isEnabled property set to false. If you want users to undo and redo, you should set that property to true once you have initialized the Diagram or its Model.

  This property setter does not raise a ChangedEvent.

## Methods

### addArrayItem

- addArrayItem(arr: any[], val: any): void

- Add an item at the end of a data array that may be data bound by a Panel as its Panel.itemArray, in a manner that can be undone/redone and that automatically updates any bindings.

  This also calls raiseChangedEvent to notify all listeners about the ChangedEvent.Insert.

  If you want to add a new node or part to the diagram, call addNodeData.

  see

    insertArrayItem

  since

    1.1

  #### Parameters

  - ##### arr: any[]

    an Array that is the value of some Panel's Panel.itemArray.

  - ##### val: any

    the new value to be pushed onto the array.

  #### Returns void

### addChangedListener

- addChangedListener(listener: (e: ChangedEvent) => void): Model

- Register an event handler that is called when there is a ChangedEvent.

  This registration does not raise a ChangedEvent. In case a Diagram's Model may be replaced, you may prefer calling Diagram.addModelChangedListener instead of this method.

  Event listeners are not written out by toJson.

  Do not add or remove Changed listeners during the execution of a Changed listener.

  see

    removeChangedListener, Diagram.addModelChangedListener

  #### Parameters

  - ##### listener: (e: ChangedEvent) => void

    a function that takes a ChangedEvent as its argument.

    - - (e: ChangedEvent): void

      - #### Parameters

        - ##### e: ChangedEvent

        #### Returns void

  #### Returns Model

  this Model

### addNodeData

- addNodeData(nodedata: ObjectData): void

- When you want to add a node or group to the diagram, call this method with a new data object. This will add that data to the nodeDataArray and notify all listeners that a new node data object has been inserted into the collection.

  To remove a node from the diagram, you can remove its data object by calling removeNodeData.

  To add or remove an object or value from an item array, call insertArrayItem or removeArrayItem.

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  #### Returns void

### addNodeDataCollection

- addNodeDataCollection(coll: ObjectData[] | Iterable<ObjectData>): void

- Add to this model all of the node data held in an Array or in an Iterable of node data objects.

  since

    1.3

  #### Parameters

  - ##### coll: ObjectData[] | Iterable<ObjectData>

    a collection of node data objects to add to the nodeDataArray

  #### Returns void

### applyIncrementalJson

- applyIncrementalJson(s: string | ObjectData): void

- Modify this model by applying the changes given in an "incremental" model change in JSON format generated by toIncrementalJson. The expected properties of the argument are described at toIncrementalJson. Incremental changes must be applied in the same order that the changes occurred in the original model.

  This requires the "incremental" property to be present and to be a number, as specified by toIncrementalJson. All of the top-level properties in the JSON, such as nodeKeyProperty, must be the same as for this model. Note that if the model is a GraphLinksModel, you will have to have set GraphLinksModel.linkKeyProperty to the name of a property, the same both in the Diagram.model as well as in the data that you pass to this method.

  This conducts a transaction.

  since

    1.6

  #### Parameters

  - ##### s: string | ObjectData

    a String in JSON format containing modifications to be performed to the model, or a JavaScript Object parsed from such a string

  #### Returns void

### assignAllDataProperties

- assignAllDataProperties(data: ObjectData, props: ObjectData): void

- This is similar to `Object.assign`, but safely calls setDataProperty for each property other than a key property. This does not delete any properties on the DATA object, although properties may be set to undefined if they are set that way on the PROPS object.

  #### Parameters

  - ##### data: ObjectData

    a data object

  - ##### props: ObjectData

    an Object holding various properties whose values are to be assigned to the DATA object

  #### Returns void

### clear

- clear(): void

- Clear out all references to any model data. This also clears out the UndoManager, so this operation is not undoable. This method is called by Diagram.clear; it does not notify any Diagrams or other listeners. This method does not unregister any Changed event listeners.

  Instead of calling this method, you may prefer to set nodeDataArray to an empty JavaScript Array. If this model is a GraphLinksModel, you would also want to set GraphLinksModel.linkDataArray to a separate empty JavaScript Array.

  #### Returns void

### Virtual cloneDeep

- cloneDeep<T>(obj: T): T

- Deeply copy an object or array and return the new object. This is typically called on a nodeDataArray or GraphLinksModel.linkDataArray or data objects within them.

  By default, this method will make deep clones of arrays and JavaScript objects and maintain any shared or cyclic references. It will properly copy any `Date` or `RegExp` object, and will call a `copy` function on any object where one exists. It also handles certain GoJS classes: `Point`, `Size`, `Rect`, `Margin`, `Spot`, `List`, `Set`, and `Map`. It will not handle instances of `Diagram`, `Layer`, `GraphObject`, `Tool`, `CommandHandler`, `AnimationManager` or subclasses or related classes.

  This method may be overridden. Please read the Introduction page on Extensions for how to override methods and how to call this base method. Only override this method when the default behavior doesn't suit the data. When cloning objects, we recommend skipping the `__gohashid` property, which is used internally.

  since

    2.1

  #### Type parameters

  - #### T

  #### Parameters

  - ##### obj: T

  #### Returns T

### Protected Virtual cloneProtected

- cloneProtected(copy: Model): void

- Copies properties from this model to the given model, which must be of the same class. This is called by copy. This method may be overridden. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

  since

    1.6

  #### Parameters

  - ##### copy: Model

  #### Returns void

### commit

- commit(func: (m: Model) => void, tname?: string): void

- Starts a new transaction, calls the provided function, and commits the transaction. Code is called within a try-finally loop. If the function does not return normally, this rolls back the transaction rather than committing it. Example usage:

      model.commit(m => m.addNodeData({ counter: myCounter++ }), "Added Node");

  since

    1.8

  #### Parameters

  - ##### func: (m: Model) => void

    the function to call as the transaction body

    - - (m: Model): void

      - #### Parameters

        - ##### m: Model

        #### Returns void

  - ##### Optional tname: string

    a descriptive name for the transaction, or null to temporarily set skipsUndoManager to true; if no string transaction name is given, an empty string is used as the transaction name

  #### Returns void

### commitTransaction

- commitTransaction(tname?: string): boolean

- Commit the changes of the current transaction. This just calls UndoManager.commitTransaction.

  #### Parameters

  - ##### Optional tname: string

    a descriptive name for the transaction.

  #### Returns boolean

  the value returned by UndoManager.commitTransaction.

### containsNodeData

- containsNodeData(nodedata: ObjectData): boolean

- Decide if a given node data object is in this model, using reference equality.

  If you do not have a reference to the particular data object that is in the nodeDataArray, you may need to search for it by iterating through that Array, or by finding the desired Node or simple Part in a Diagram and getting that node's Panel.data, or most likely by calling findNodeDataForKey.

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  #### Returns boolean

  true if it is a node data object in this model; false otherwise.

### Virtual copy

- copy(): Model

- Creates a shallow copy of this Model and returns it. The data are not copied: nodeDataArray, modelData, GraphLinksModel.linkDataArray, GraphLinksModel.archetypeNodeData are left empty. Nor are any Changed listeners or the UndoManager copied.

  since

    1.6

  #### Returns Model

  an empty copy of the model with the same properties, other than data

### Virtual copyNodeData

- copyNodeData(nodedata: ObjectData): ObjectData

- Make a copy of a node data object. This uses the value of copyNodeDataFunction to actually perform the copy, unless that property is null. When it is null the default behavior is to just make a shallow copy of the JavaScript Object.

  However when copiesArrays is true, this will make a copy of property values that are JavaScript Arrays. This is useful when you do not want the Arrays to be shared between the node data objects. Note that if you want to copy some property values that are Arrays but not other properties that are Arrays, you cannot use copiesArrays but must implement your own copyNodeDataFunction.

  In addition when copiesArrayObjects is true, if items in the Array being copied are JavaScript Objects, those objects are copied, recursively. This is useful when the items in copied Arrays are themselves objects that need to be copied. Note that if you want to share references to some but not all of the objects in copied Arrays you cannot use copiesArrayObjects but must implement your own copyNodeDataFunction.

  This does not modify the model -- the returned data object is not added to this model. This assumes that the data's constructor can be called with no arguments.

  Models should not have any references to Diagrams or GraphObjects or Tools or Layouts or other objects that form a Diagram.

  Warning: there should not be any cyclical references within the model data, unless you either do not turn on copiesArrays or copiesArrayObjects or unless you have supplied your own copyNodeDataFunction that can handle cyclical references.

  see

    addNodeData

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  #### Returns ObjectData

### findNodeDataForKey

- findNodeDataForKey(key: Key): ObjectData

- Given a number or string, find the node data object in this model that uses the given value as its unique key.

  see

    containsNodeData, getKeyForNodeData

  #### Parameters

  - ##### key: Key

    a string or a number.

  #### Returns ObjectData

  null if the key is not present in the model, or if the key is null or undefined or not a string or number.

### getCategoryForNodeData

- getCategoryForNodeData(nodedata: ObjectData): string

- Find the category of a given node data, a string naming the node template or group template or part template that the Diagram should use to represent the node data.

  see

    nodeCategoryProperty, setCategoryForNodeData

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  #### Returns string

### getKeyForNodeData

- getKeyForNodeData(nodedata: ObjectData): Key

- Given a node data object return its unique key: a number or a string. This returns undefined if there is no key value.

  It is possible to change the key for a node data object by calling setKeyForNodeData.

  see

    nodeKeyProperty, setKeyForNodeData, findNodeDataForKey

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  #### Returns Key

### insertArrayItem

- insertArrayItem(arr: any[], idx: number, val: any): void

- Add an item to a data array that may be data bound by a Panel as its Panel.itemArray, given a new data value and the index at which to insert the new value, in a manner that can be undone/redone and that automatically updates any bindings.

  This also calls raiseChangedEvent to notify all listeners about the ChangedEvent.Insert.

  If you want to add a new node or part to the diagram, call addNodeData.

  see

    removeArrayItem

  #### Parameters

  - ##### arr: any[]

    an Array that is the value of some Panel's Panel.itemArray.

  - ##### idx: number

    the zero-based array index where the new value will be inserted; use -1 to push the new value on the end of the array.

  - ##### val: any

    the new value to be inserted into the array.

  #### Returns void

### makeNodeDataKeyUnique

- makeNodeDataKeyUnique(nodedata: ObjectData): void

- This method is called when a node data object is added to the model to make sure that getKeyForNodeData returns a unique key value.

  The key value should be unique within the set of data managed by this model: nodeDataArray. If the key is already in use, this will assign an unused number to the nodeKeyProperty property on the data.

  If you want to customize the way in which node data gets a unique key, you can set the makeUniqueKeyFunction functional property.

  If the node data object is already in the model and you want to change its key value, call setKeyForNodeData and give it a new unique key value.

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  #### Returns void

### mergeNodeDataArray

- mergeNodeDataArray(arr: ObjectData[]): void

- Take an Array of node data objects and update nodeDataArray without replacing the Array and without replacing any existing node data objects that are identified by key.

  For node data objects that have the same key value, this makes calls to setDataProperty to update the existing node data object. For new keys, this calls cloneDeep to copy the data and then addNodeData to add a new node to the model. For existing nodes that have keys that are not present in the given Array, this calls removeNodeData to remove the existing node from the model.

  This method is typically used when GoJS is being used within an application that is maintaining state related to the diagram model. When state is updated, this method can be called to keep the GoJS model synchronized. Any updates to the data should use new references since this method will use reference equality to check if a node data object needs to be updated.

  This method does not conduct a transaction.

  since

    2.1

  #### Parameters

  - ##### arr: ObjectData[]

  #### Returns void

### raiseChangedEvent

- raiseChangedEvent(change: EnumValue, propertyname: string | ((obj: ObjectData, val: any) => any), obj: ObjectData, oldval: any, newval: any, oldparam?: any, newparam?: any): void

- Call this method to notify that the model or its objects have changed. This constructs a ChangedEvent and calls all Changed listeners.

  #### Parameters

  - ##### change: EnumValue

    specifies the general nature of the change; typically the value is ChangedEvent.Property.

  - ##### propertyname: string | ((obj: ObjectData, val: any) => any)

    names the property that was modified, or a function that takes an Object and returns the property value.

  - ##### obj: ObjectData

    the object that was modified, typically a GraphObject, Diagram, or a Model.

  - ##### oldval: any

    the previous or older value.

  - ##### newval: any

    the next or newer value.

  - ##### Optional oldparam: any

    an optional value that helps describe the older value.

  - ##### Optional newparam: any

    an optional value that helps describe the newer value.

  #### Returns void

### raiseDataChanged

- raiseDataChanged(data: ObjectData, propertyname: string | ((obj: ObjectData, val: any) => any), oldval: any, newval: any, oldparam?: any, newparam?: any): void

- Call this method to notify about a data property having changed value. This constructs a ChangedEvent and calls all Changed listeners.

  You should call this method only if the property value actually changed. This method is called by setDataProperty.

  #### Parameters

  - ##### data: ObjectData

    the data object whose property changed value.

  - ##### propertyname: string | ((obj: ObjectData, val: any) => any)

    the name of the property, or a function that takes an Object and returns the property value.

  - ##### oldval: any

    the previous or old value for the property.

  - ##### newval: any

    the next or new value for the property.

  - ##### Optional oldparam: any

    an optional value additionally describing the old value.

  - ##### Optional newparam: any

    an optional value additionally describing the new value.

  #### Returns void

### removeArrayItem

- removeArrayItem(arr: any[], idx?: number): void

- Remove an item from a data array that may be data bound by a Panel as its Panel.itemArray, given the index at which to remove a data value, in a manner that can be undone/redone and that automatically updates any bindings.

  This also calls raiseChangedEvent to notify all listeners about the ChangedEvent.Remove.

  If you want to remove a node from the diagram, call removeNodeData.

  Note that there is no version of this method that takes an item value instead of an index into the array. Because item arrays may hold any JavaScript value, including numbers and strings, there may be duplicate entries with that value in the array. To avoid ambiguity, removing an item from an array requires an index.

  see

    insertArrayItem

  #### Parameters

  - ##### arr: any[]

    an Array that is the value of some Panel's Panel.itemArray.

  - ##### Optional idx: number

    the zero-based array index of the data item to be removed from the array; if not supplied it will remove the last item of the array.

  #### Returns void

### removeChangedListener

- removeChangedListener(listener: (e: ChangedEvent) => void): void

- Unregister an event handler listener.

  This deregistration does not raise a ChangedEvent. In case a Diagram's Model may be replaced, you may prefer calling Diagram.removeModelChangedListener instead of this method.

  see

    addChangedListener, Diagram.removeModelChangedListener

  #### Parameters

  - ##### listener: (e: ChangedEvent) => void

    a function that takes a ChangedEvent as its argument.

    - - (e: ChangedEvent): void

      - #### Parameters

        - ##### e: ChangedEvent

        #### Returns void

### removeNodeData

- removeNodeData(nodedata: ObjectData): void

- When you want to remove a node or group from the diagram, call this method with an existing data object. This will remove that data from the nodeDataArray and notify all listeners that a node data object has been removed from the collection.

  If you do not have a reference to the particular data object that is in the nodeDataArray, you may need to search for it by iterating through that Array, or by finding the desired Node or simple Part in a Diagram and getting that node's Panel.data, or most likely by calling findNodeDataForKey.

  Removing a node data from a model does not automatically remove any connected link data from the model. Removing a node data that represents a group does not automatically remove any member node data or link data from the model.

  To add a node to the diagram, you can add its data object by calling addNodeData.

  To add or remove an object or value from an item array, call insertArrayItem or removeArrayItem.

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  #### Returns void

### removeNodeDataCollection

- removeNodeDataCollection(coll: ObjectData[] | Iterable<ObjectData>): void

- Remove from this model all of the node data held in an Array or in an Iterable of node data objects.

  since

    1.3

  #### Parameters

  - ##### coll: ObjectData[] | Iterable<ObjectData>

    a collection of node data objects to remove from the nodeDataArray

  #### Returns void

### rollbackTransaction

- rollbackTransaction(): boolean

- Rollback the current transaction, undoing any recorded changes. This just calls UndoManager.rollbackTransaction.

  #### Returns boolean

  the value returned by UndoManager.rollbackTransaction.

### set

- set(data: ObjectData, propname: string, val: any): void

- A synonym for setDataProperty

  see

    setDataProperty

  since

    1.8

  #### Parameters

  - ##### data: ObjectData

    a JavaScript object typically the value of a Panel.data and represented by a Node, Link, Group, simple Part, or item in a Panel.itemArray; or this model's modelData.

  - ##### propname: string

    a string that is not null or the empty string.

  - ##### val: any

    the new value for the property.

  #### Returns void

### setCategoryForNodeData

- setCategoryForNodeData(nodedata: ObjectData, cat: string): void

- Change the category of a given node data, a string naming the node template or group template or part template that the Diagram should use to represent the node data.

  Changing the node template for a node data will cause the existing Node, Group, or Part to be replaced with a new instance of the same class created by copying the new node template and applying any data-bindings. That means that the templates in the Diagram.nodeTemplateMap or Diagram.groupTemplateMap must be instances of the same class -- one cannot convert a Node into a Group or vice-versa by setting the category.

  Binding sources should not be (or depend in a conversion function on) the category of the data if you might be modifying the category, because then some bindings might be evaluated before or after the category has been changed.

  see

    nodeCategoryProperty, getCategoryForNodeData

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  - ##### cat: string

    Must not be null.

  #### Returns void

### Virtual setDataProperty

- setDataProperty(data: ObjectData, propname: string, val: any): void

- Change the value of some property of a node data, a link data, an item data, or the Model.modelData, given a string naming the property and the new value, in a manner that can be undone/redone and that automatically updates any bindings.

  This gets the old value of the property; if the value is the same as the new value, no side-effects occur. This calls raiseDataChanged to notify about the change.

  Note that it is insufficient to modify an item Array (for example by pushing a new item onto the Array) and then calling `setDataProperty(data, "items", data.items)` because the value of `data.items` is still the same reference. Instead you will want to call insertArrayItem, addArrayItem, or removeArrayItem.

  If you modify the property that is the nodeKeyProperty, this will call setKeyForNodeData.

  If you modify the property that is the nodeCategoryProperty or the GraphLinksModel.linkCategoryProperty, this will call setCategoryForNodeData or GraphLinksModel.setCategoryForLinkData. But if the category might change, Binding sources should not be (or depend in a conversion function on) the category of the data, because then some bindings might be evaluated before or after the category has been changed.

  see

    set

  #### Parameters

  - ##### data: ObjectData

    a JavaScript object typically the value of a Panel.data and represented by a Node, Link, Group, simple Part, or item in a Panel.itemArray; or this model's modelData.

  - ##### propname: string

    a string that is not null or the empty string.

  - ##### val: any

    the new value for the property.

  #### Returns void

### setKeyForNodeData

- setKeyForNodeData(nodedata: ObjectData, key: Key): void

- Change the unique key of a given node data that is already in this model. The new key value must be unique -- i.e. not in use by another node data object. You can call findNodeDataForKey to check if a proposed new key is already in use.

  This operation will check all data objects in the model and replace all references using the old key value with the new one.

  If this is called on a node data object that is not (yet) in this model, this unconditionally modifies the property to the new key value.

  see

    nodeKeyProperty, getKeyForNodeData

  since

    1.1

  #### Parameters

  - ##### nodedata: ObjectData

    a JavaScript object represented by a node, group, or non-link.

  - ##### key: Key

  #### Returns void

### startTransaction

- startTransaction(tname?: string): boolean

- Begin a transaction, where the changes are held by a Transaction object in the UndoManager. This just calls UndoManager.startTransaction.

  see

    commit

  #### Parameters

  - ##### Optional tname: string

    a descriptive name for the transaction.

  #### Returns boolean

  the value returned by UndoManager.startTransaction.

### toIncrementalData

- toIncrementalData(e: ChangedEvent): IncrementalData

- Produce an object representing the changes in the most recent Transaction. The structure of the object follows the same format as the JSON output from toIncrementalJson.

  Note that these incremental changes include the results of undo and redo operations.

  For GraphLinksModels, this method requires that GraphLinksModel.linkKeyProperty is not an empty string.

  Any node or link data objects contained in the "modified..." properties will be deep copies of the data in the model. The objects will contain proper copies of certain GoJS classes, and some common built-in objects such as Dates and RegExps. Other classes will just be copied as plain Javascript objects, so it is best to avoid using special classes in one's data.

  This method is most commonly used when GoJS must communicate with some external data source and maintain integrity between the two while avoiding serialization/deserialization.

        myDiagram.addModelChangedListener(e => {
          if (e.isTransactionFinished) {
            var dataChanges = e.model.toIncrementalData(e);
            ... update React state/save to database ...
          }
        });

  Caution: don't call JSON.stringify on the resulting object, because that will not properly handle any instances of JavaScript classes that are referenced by the object's properties. Instead call toIncrementalJson, which will produce a more compact textual serialization.

  see

    toIncrementalJson

  since

    2.1

  #### Parameters

  - ##### e: ChangedEvent

    a Transaction ChangedEvent for which ChangedEvent.isTransactionFinished is true

  #### Returns IncrementalData

  returns either null if no changes occurred, or an object containing incremental model changes for the given Transaction

### toIncrementalJson

- toIncrementalJson(e: ChangedEvent, classname?: string): string

- Produce a JSON-format string representing the changes in the most recent Transaction. This writes out JSON for a model, but recording only changes in the given Transaction, with the addition of the "incremental" property to mark it as different from a complete model. Instead of the "nodeDataArray" property (and "linkDataArray" property for GraphLinksModels), this will have "inserted...", "modified...", and "removed..." properties that are non-empty Arrays.

  The "modifiedNodeData" Array holds JavaScript objects. The "insertedNodeKeys" and "removedNodeKeys" Arrays hold keys (numbers or strings) of data, not whole objects, that have been added and/or deleted. The "modelData" property holds the Model.modelData object, if it was modified.

  Note that it is entirely plausible for the same object be in or referenced by all three Arrays, because a single Transaction can include adding a node, modifying it, and removing it.

  The purpose of this method is to make it easier to send incremental changes to the server/database, instead of sending the whole model. Whereas it has always been easy to perform "batch" updates or "file saves":

        myDiagram.addModelChangedListener(e => {
          if (e.isTransactionFinished) {
            var json = e.model.toJson();
            // save the whole model upon each transaction completion or undo/redo
            ... send to server/database ...
          }
        });

  You can now easily send "incremental" updates:

        myDiagram.addModelChangedListener(e => {
          if (e.isTransactionFinished) {
            var json = e.model.toIncrementalJson(e);
            // record each Transaction as a JSON-format string
            ... send to server/database ...
          }
        });

  Note that these incremental changes include the results of undo and redo operations. Also, when you might call applyIncrementalJson, you will need to disable your Changed listener, so that it does not send spurious changes to your database during the process of apply incremental changes from the database.

  For GraphLinksModels, this method requires that GraphLinksModel.linkKeyProperty is not an empty string. The incremental JSON for GraphLinksModels will include "modifiedLinkData", "insertedLinkKeys", and "removedLinkKeys" properties that are non-empty Arrays.

  The same restrictions on data property names and data property values applies to this method as it does to toJson.

  since

    1.6

  #### Parameters

  - ##### e: ChangedEvent

    a Transaction ChangedEvent for which ChangedEvent.isTransactionFinished is true

  - ##### Optional classname: string

    for the written model, defaults to the name of the class of the model

  #### Returns string

### toJson

- toJson(classname?: string): string

- Generate a string representation of the persistent data in this model, in JSON format, that can be read in later with a call to Model.fromJson.

  Object properties that are not enumerable or whose names start with "_" are not written out.

  Functions are not able to be written in JSON format, so any properties that have function values will not be saved in the JSON string.

  There must not be any circular references within the model data. Any sharing of object references will be lost in the written JSON.

  Most object classes cannot be serialized into JSON without special knowledge and processing at both ends. The toJson and Model.fromJson methods automatically do such processing for numbers that are NaN and for objects that are of class Point, Size, Rect, Margin, Spot, Brush (but not for brush patterns), and for Geometry. For instances of those classes, special objects are written out with a property named "class" whose value will be one of the special cases that will be substituted by Model.fromJson: "NaN", "Date", "go.EnumValue", "go.Point", "go.Size", "go.Rect", "go.Margin", "go.Spot", "go.Brush", "go.Geometry".

  However, we recommend that you use Binding converters (static functions named "parse" and "stringify") to represent Points, Sizes, Rects, Margins, Spots, and Geometries as string values in your data, rather than as Objects. This makes the JSON text smaller and simpler and easier to read.

  As a special case when serializing an object, if the property is named "points" and the property value is a List of Points, it will write an Array of numbers.

  Note that this is a method on the Model class. It cannot render unmodeled Parts such as the background grid or any Parts that you have added directly to a Diagram.

  Typical usage:

      var modelAsText = myDiagram.model.toJson();
      // now save this text string by sending it to your database

  #### Parameters

  - ##### Optional classname: string

    The optional name of the model class to use in the output; for the standard models, this is their class name prefixed with "go.".

  #### Returns string

  a String in JSON format containing all of the persistent properties of the model.

### updateTargetBindings

- updateTargetBindings(data: ObjectData, srcpropname?: string): void

- Find a Part corresponding to the given data and call its Panel.updateTargetBindings method, in each Diagram that uses this Model.

  Caution: setting a data property without calling setDataProperty and then calling this updateTargetBindings method will update GraphObjects that are bound to the property, but such data settings will not be recorded in the UndoManager and therefore will not be undone/redone, causing an inconsistency between the GraphObjects and the part data.

  #### Parameters

  - ##### data: ObjectData

    The data object in this model that was modified.

  - ##### Optional srcpropname: string

    If not present or the empty string, update all bindings on the target Part or item Panel otherwise update only those bindings using this source property name.

  #### Returns void

### Static fromJson

- fromJson(s: string | ObjectData, model?: Model): Model

- This static function parses a string in JSON format that was written by Model.toJson, and then constructs, initializes, and returns a model with that information.

  Note that properties with values that are functions are not written out by toJson, so reading in such a model will require constructing such a model, initializing its functional property values, and explicitly passing it in as the second argument.

  In order to serialize instances of some classes and enumerated values and some other cases, Model.toJson writes out special Objects that this Model.fromJson function substitutes with the intended values. Those special objects will have a property named "class" whose value will be one of the special substitution cases: "NaN", "Date", "go.EnumValue", "go.Point", "go.Size", "go.Rect", "go.Margin", "go.Spot", "go.Brush", "go.Geometry".

  As a special case when deserializing an object, if the property is named "points" and the property value is an Array with an even number of numbers, it will substitute a List of Points.

  Typical usage:

      var modelAsText = ...;  // fetch the model in textual format from a database
      myDiagram.model = go.Model.fromJson(modelAsText);

  #### Parameters

  - ##### s: string | ObjectData

    a String in JSON format containing all of the persistent properties of the model, or an Object already read from JSON text.

  - ##### Optional model: Model

    an optional model to be modified; if not supplied, it constructs and returns a new model whose name is specified by the "class" property.

  #### Returns Model

  the supplied or created model loaded with data from the given string.

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