---
title: Tree
lang: en-US
---

# Tree

Display a set of data with hierarchies.

## Basic usage

Basic tree structure.

:::demo

tree/basic

:::

## Selectable

Used for node selection.

:::demo This example also shows how to load node data asynchronously.

tree/selectable

:::

## Custom leaf node in lazy mode

:::demo A node's data is not fetched until it is clicked, so the Tree cannot predict whether a node is a leaf node. That's why a drop-down button is added to each node, and if it is a leaf node, the drop-down button will disappear when clicked. That being said, you can also tell the Tree in advance whether the node is a leaf node, avoiding the render of the drop-down button before a leaf node.

tree/custom-leaf

:::

## Disabled checkbox

The checkbox of a node can be set as disabled.

:::demo In the example, 'disabled' property is declared in defaultProps, and some nodes are set as 'disabled:true'. The corresponding checkboxes are disabled and can't be clicked.

tree/disabled

:::

## Default expanded and default checked

Tree nodes can be initially expanded or checked

:::demo Use `default-expanded-keys` and `default-checked-keys` to set initially expanded and initially checked nodes respectively. Note that for them to work, `node-key` is required. Its value is the name of a key in the data object, and the value of that key should be unique across the whole tree.

tree/default-state

:::

## Checking tree nodes

:::demo This example shows how to get and set checked nodes. They both can be done in two approaches: node and key. If you are taking the key approach, `node-key` is required.

tree/checking-tree

:::

## Custom node content

The content of tree nodes can be customized, so you can add icons or buttons as you will

:::demo There are two ways to customize template for tree nodes: `render-content` and scoped slot. Use `render-content` to assign a render function that returns the content of tree nodes. See Vue's documentation for a detailed introduction of render functions. If you prefer scoped slot, you'll have access to `node` and `data` in the scope, standing for the TreeNode object and node data of the current node respectively. Note that the `render-content` demo can't run in jsfiddle because it doesn't support JSX syntax. In a real project, `render-content` will work if relevant dependencies are correctly configured.

tree/customized-node

:::

## Custom node class

The class of tree nodes can be customized

:::demo. Use `props.class` to build class name of nodes.

tree/custom-node-class

:::

## Tree node filtering

Tree nodes can be filtered

:::demo Invoke the `filter` method of the Tree instance to filter tree nodes. Its parameter is the filtering keyword. Note that for it to work, `filter-node-method` is required, and its value is the filtering method.

tree/filtering

:::

## Accordion

Only one node among the same level can be expanded at one time.

:::demo

tree/accordion

:::

## Draggable

You can drag and drop Tree nodes by adding a `draggable` attribute.

:::demo

tree/draggable

:::

## Attributes

| Attribute             | Description                                                                                                                                                                                                                                                                                                                                                                 | Type                                   | Accepted Values | Default |
| --------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------- | --------------- | ------- |
| data                  | tree data                                                                                                                                                                                                                                                                                                                                                                   | array                                  | —               | —       |
| empty-text            | text displayed when data is void                                                                                                                                                                                                                                                                                                                                            | string                                 | —               | —       |
| node-key              | unique identity key name for nodes, its value should be unique across the whole tree                                                                                                                                                                                                                                                                                        | string                                 | —               | —       |
| props                 | configuration options, see the following table                                                                                                                                                                                                                                                                                                                              | object                                 | —               | —       |
| render-after-expand   | whether to render child nodes only after a parent node is expanded for the first time                                                                                                                                                                                                                                                                                       | boolean                                | —               | true    |
| load                  | method for loading subtree data, only works when `lazy` is true                                                                                                                                                                                                                                                                                                             | function(node, resolve)                | —               | —       |
| render-content        | render function for tree node                                                                                                                                                                                                                                                                                                                                               | Function(h, `{ node, data, store }`)   | —               | —       |
| highlight-current     | whether current node is highlighted                                                                                                                                                                                                                                                                                                                                         | boolean                                | —               | false   |
| default-expand-all    | whether to expand all nodes by default                                                                                                                                                                                                                                                                                                                                      | boolean                                | —               | false   |
| expand-on-click-node  | whether to expand or collapse node when clicking on the node, if false, then expand or collapse node only when clicking on the arrow icon.                                                                                                                                                                                                                                  | boolean                                | —               | true    |
| check-on-click-node   | whether to check or uncheck node when clicking on the node, if false, the node can only be checked or unchecked by clicking on the checkbox.                                                                                                                                                                                                                                | boolean                                | —               | false   |
| auto-expand-parent    | whether to expand father node when a child node is expanded                                                                                                                                                                                                                                                                                                                 | boolean                                | —               | true    |
| default-expanded-keys | array of keys of initially expanded nodes                                                                                                                                                                                                                                                                                                                                   | array                                  | —               | —       |
| show-checkbox         | whether node is selectable                                                                                                                                                                                                                                                                                                                                                  | boolean                                | —               | false   |
| check-strictly        | whether checked state of a node not affects its father and child nodes when `show-checkbox` is `true`                                                                                                                                                                                                                                                                       | boolean                                | —               | false   |
| default-checked-keys  | array of keys of initially checked nodes                                                                                                                                                                                                                                                                                                                                    | array                                  | —               | —       |
| current-node-key      | key of initially selected node                                                                                                                                                                                                                                                                                                                                              | string, number                         | —               | —       |
| filter-node-method    | this function will be executed on each node when use filter method. if return `false`, tree node will be hidden.                                                                                                                                                                                                                                                            | Function(value, data, node)            | —               | —       |
| accordion             | whether only one node among the same level can be expanded at one time                                                                                                                                                                                                                                                                                                      | boolean                                | —               | false   |
| indent                | horizontal indentation of nodes in adjacent levels in pixels                                                                                                                                                                                                                                                                                                                | number                                 | —               | 16      |
| icon                  | custome tree node icon component                                                                                                                                                                                                                                                                                                                                            | string / Component                     | -               | -       |
| lazy                  | whether to lazy load leaf node, used with `load` attribute                                                                                                                                                                                                                                                                                                                  | boolean                                | —               | false   |
| draggable             | whether enable tree nodes drag and drop                                                                                                                                                                                                                                                                                                                                     | boolean                                | —               | false   |
| allow-drag            | this function will be executed before dragging a node. If `false` is returned, the node can not be dragged                                                                                                                                                                                                                                                                  | Function(node)                         | —               | —       |
| allow-drop            | this function will be executed before the dragging node is dropped. If `false` is returned, the dragging node can not be dropped at the target node. `type` has three possible values: 'prev' (inserting the dragging node before the target node), 'inner' (inserting the dragging node to the target node) and 'next' (inserting the dragging node after the target node) | Function(draggingNode, dropNode, type) | —               | —       |

## props

| Attribute | Description                                                                   | Type                         | Accepted Values | Default |
| --------- | ----------------------------------------------------------------------------- | ---------------------------- | --------------- | ------- |
| label     | specify which key of node object is used as the node's label                  | string, function(data, node) | —               | —       |
| children  | specify which node object is used as the node's subtree                       | string                       | —               | —       |
| disabled  | specify which key of node object represents if node's checkbox is disabled    | string, function(data, node) | —               | —       |
| isLeaf    | specify whether the node is a leaf node, only works when lazy load is enabled | string, function(data, node) | —               | —       |
| class     | custom node class name                                                        | string, function(data, node) | —               | —       |

## Method

`Tree` has the following method, which returns the currently selected array of nodes.
| Method | Description | Parameters |
| --------------- | ---------------------------------------- | ---------------------------------------- |
| filter | filter all tree nodes, filtered nodes will be hidden | Accept a parameter which will be used as first parameter for filter-node-method |
| updateKeyChildren | set new data to node, only works when `node-key` is assigned | (key, data) Accept two parameters: 1. key of node 2. new data |
| getCheckedNodes | If the node can be selected (`show-checkbox` is `true`), it returns the currently selected array of nodes | (leafOnly, includeHalfChecked) Accept two boolean type parameters: 1. default value is `false`. If the parameter is `true`, it only returns the currently selected array of sub-nodes. 2. default value is `false`. If the parameter is `true`, the return value contains halfchecked nodes |
| setCheckedNodes | set certain nodes to be checked, only works when `node-key` is assigned | an array of nodes to be checked |
| getCheckedKeys | If the node can be selected (`show-checkbox` is `true`), it returns the currently selected array of node's keys | (leafOnly) Accept a boolean type parameter whose default value is `false`. If the parameter is `true`, it only returns the currently selected array of sub-nodes. |
| setCheckedKeys | set certain nodes to be checked, only works when `node-key` is assigned | (keys, leafOnly) Accept two parameters: 1. an array of node's keys to be checked 2. a boolean type parameter whose default value is `false`. If the parameter is `true`, it only returns the currently selected array of sub-nodes. |
| setChecked | set node to be checked or not, only works when `node-key` is assigned | (key/data, checked, deep) Accept three parameters: 1. node's key or data to be checked 2. a boolean typed parameter indicating checked or not. 3. a boolean typed parameter indicating deep or not. |
| getHalfCheckedNodes | If the node can be selected (`show-checkbox` is `true`), it returns the currently half selected array of nodes | - |
| getHalfCheckedKeys | If the node can be selected (`show-checkbox` is `true`), it returns the currently half selected array of node's keys | - |
| getCurrentKey | return the highlight node's key (null if no node is highlighted) | — |
| getCurrentNode | return the highlight node's data (null if no node is highlighted) | — |
| setCurrentKey | set highlighted node by key, only works when `node-key` is assigned | (key, shouldAutoExpandParent=true) 1. the node's key to be highlighted. If `null`, cancel the currently highlighted node 2. whether to automatically expand parent node |
| setCurrentNode | set highlighted node, only works when `node-key` is assigned | (node, shouldAutoExpandParent=true) 1. the node to be highlighted 2. whether to automatically expand parent node |
| getNode | get node by data or key | (data) the node's data or key |
| remove | remove a node, only works when node-key is assigned | (data) the node's data or node to be deleted |
| append | append a child node to a given node in the tree | (data, parentNode) 1. child node's data to be appended 2. parent node's data, key or node |
| insertBefore | insert a node before a given node in the tree | (data, refNode) 1. node's data to be inserted 2. reference node's data, key or node |
| insertAfter | insert a node after a given node in the tree | (data, refNode) 1. node's data to be inserted 2. reference node's data, key or node |

## Events

| Event Name       | Description                                               | Parameters                                                                                                                                                                                       |
| ---------------- | --------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| node-click       | triggers when a node is clicked                           | three parameters: node object corresponding to the node clicked, `node` property of TreeNode, TreeNode itself, event object                                                                      |
| node-contextmenu | triggers when a node is clicked by right button           | four parameters: event, node object corresponding to the node clicked, `node` property of TreeNode, TreeNode itself                                                                              |
| check-change     | triggers when the selected state of the node changes      | three parameters: node object corresponding to the node whose selected state is changed, whether the node is selected, whether node's subtree has selected nodes                                 |
| check            | triggers after clicking the checkbox of a node            | two parameters: node object corresponding to the node that is checked / unchecked, tree checked status object which has four props: checkedNodes, checkedKeys, halfCheckedNodes, halfCheckedKeys |
| current-change   | triggers when current node changes                        | two parameters: node object corresponding to the current node, `node` property of TreeNode                                                                                                       |
| node-expand      | triggers when current node open                           | three parameters: node object corresponding to the node opened, `node` property of TreeNode, TreeNode itself                                                                                     |
| node-collapse    | triggers when current node close                          | three parameters: node object corresponding to the node closed, `node` property of TreeNode, TreeNode itself                                                                                     |
| node-drag-start  | triggers when dragging starts                             | two parameters: node object corresponding to the dragging node, event.                                                                                                                           |
| node-drag-enter  | triggers when the dragging node enters another node       | three parameters: node object corresponding to the dragging node, node object corresponding to the entering node, event.                                                                         |
| node-drag-leave  | triggers when the dragging node leaves a node             | three parameters: node object corresponding to the dragging node, node object corresponding to the leaving node, event.                                                                          |
| node-drag-over   | triggers when dragging over a node (like mouseover event) | three parameters: node object corresponding to the dragging node, node object corresponding to the dragging over node, event.                                                                    |
| node-drag-end    | triggers when dragging ends                               | four parameters: node object corresponding to the dragging node, node object corresponding to the dragging end node (may be `undefined`), node drop type (before / after / inner), event.        |
| node-drop        | triggers after the dragging node is dropped               | four parameters: node object corresponding to the dragging node, node object corresponding to the dropped node, node drop type (before / after / inner), event.                                  |

## Slots

| Name | Description                                                            |
| ---- | ---------------------------------------------------------------------- |
| —    | Custom content for tree nodes. The scope parameter is `{ node, data }` |
