## ツリー

データの集合を階層化して表示します。

### 基本的な使い方

基本的なツリー構造。

:::demo
```html
<el-tree :data="data" :props="defaultProps" @node-click="handleNodeClick"></el-tree>

<script>
  export default {
    data() {
      return {
        data: [{
          label: 'Level one 1',
          children: [{
            label: 'Level two 1-1',
            children: [{
              label: 'Level three 1-1-1'
            }]
          }]
        }, {
          label: 'Level one 2',
          children: [{
            label: 'Level two 2-1',
            children: [{
              label: 'Level three 2-1-1'
            }]
          }, {
            label: 'Level two 2-2',
            children: [{
              label: 'Level three 2-2-1'
            }]
          }]
        }, {
          label: 'Level one 3',
          children: [{
            label: 'Level two 3-1',
            children: [{
              label: 'Level three 3-1-1'
            }]
          }, {
            label: 'Level two 3-2',
            children: [{
              label: 'Level three 3-2-1'
            }]
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    },
    methods: {
      handleNodeClick(data) {
        console.log(data);
      }
    }
  };
</script>
```
:::

### 選択可能

ノードの選択に使用します。

:::demo この例では、ノードデータを非同期にロードする方法も示しています。
```html
<el-tree
  :props="props"
  :load="loadNode"
  lazy
  show-checkbox
  @check-change="handleCheckChange">
</el-tree>

<script>
  export default {
    data() {
      return {
        props: {
          label: 'name',
          children: 'zones'
        },
        count: 1
      };
    },
    methods: {
      handleCheckChange(data, checked, indeterminate) {
        console.log(data, checked, indeterminate);
      },
      handleNodeClick(data) {
        console.log(data);
      },
      loadNode(node, resolve) {
        if (node.level === 0) {
          return resolve([{ name: 'Root1' }, { name: 'Root2' }]);
        }
        if (node.level > 3) return resolve([]);

        var hasChild;
        if (node.data.name === 'region1') {
          hasChild = true;
        } else if (node.data.name === 'region2') {
          hasChild = false;
        } else {
          hasChild = Math.random() > 0.5;
        }

        setTimeout(() => {
          var data;
          if (hasChild) {
            data = [{
              name: 'zone' + this.count++
            }, {
              name: 'zone' + this.count++
            }];
          } else {
            data = [];
          }

          resolve(data);
        }, 500);
      }
    }
  };
</script>
```
:::

### 遅延モードでのカスタムリーフノード

:::demo ノードのデータはクリックされるまで取得されないので、ツリーはそのノードがリーフノードであるかどうかを予測することができません。そのため、各ノードにはドロップダウンボタンが追加されており、リーフノードであればクリックされるとドロップダウンボタンは消えてしまいます。つまり、ノードがリーフノードであるかどうかを事前にツリーに伝えることで、リーフノードの前にドロップダウンボタンがレンダリングされるのを避けることもできます。
```html
<el-tree
  :props="props"
  :load="loadNode"
  lazy
  show-checkbox>
</el-tree>

<script>
  export default {
    data() {
      return {
        props: {
          label: 'name',
          children: 'zones',
          isLeaf: 'leaf'
        },
      };
    },
    methods: {
      loadNode(node, resolve) {
        if (node.level === 0) {
          return resolve([{ name: 'region' }]);
        }
        if (node.level > 1) return resolve([]);

        setTimeout(() => {
          const data = [{
            name: 'leaf',
            leaf: true
          }, {
            name: 'zone'
          }];

          resolve(data);
        }, 500);
      }
    }
  };
</script>
```
:::

### チェックボックス無効化

ノードのチェックボックスを無効に設定することができます。

:::demo この例では、defaultPropsで'disabled'プロパティが宣言されており、一部のノードは'disabled:true'として設定されています。対応するチェックボックスは無効化されており、クリックできないようになっています。
```html
<el-tree
  :data="data"
  :props="defaultProps"
  show-checkbox
  @check-change="handleCheckChange">
</el-tree>

<script>
  export default {
    data() {
      return {
        data: [{
          id: 1,
          label: 'Level one 1',
          children: [{
            id: 3,
            label: 'Level two 2-1',
            children: [{
              id: 4,
              label: 'Level three 3-1-1'
            }, {
              id: 5,
              label: 'Level three 3-1-2',
              disabled: true
            }]
          }, {
            id: 2,
            label: 'Level two 2-2',
            disabled: true,
            children: [{
              id: 6,
              label: 'Level three 3-2-1'
            }, {
              id: 7,
              label: 'Level three 3-2-2',
              disabled: true
            }]
          }]
        }],
        defaultProps: {
            children: 'children',
            label: 'label',
            disabled: 'disabled',
        },
      };
    }
  };
</script>
```
:::

### デフォルト展開、チェック
ツリーノードは、最初に展開またはチェックすることができます。

:::demo `default-expanded-keys` と `default-checked-keys` を用いて、それぞれ初期展開ノードと初期チェックノードを設定する。これらが動作するためには `node-key` が必要であることに注意してください。この値はデータオブジェクトのキーの名前であり、そのキーの値はツリー全体で一意でなければなりません。
```html
<el-tree
  :data="data"
  show-checkbox
  node-key="id"
  :default-expanded-keys="[2, 3]"
  :default-checked-keys="[5]"
  :props="defaultProps">
</el-tree>

<script>
  export default {
    data() {
      return {
        data: [{
          id: 1,
          label: 'Level one 1',
          children: [{
            id: 4,
            label: 'Level two 1-1',
            children: [{
              id: 9,
              label: 'Level three 1-1-1'
            }, {
              id: 10,
              label: 'Level three 1-1-2'
            }]
          }]
        }, {
          id: 2,
          label: 'Level one 2',
          children: [{
            id: 5,
            label: 'Level two 2-1'
          }, {
            id: 6,
            label: 'Level two 2-2'
          }]
        }, {
          id: 3,
          label: 'Level one 3',
          children: [{
            id: 7,
            label: 'Level two 3-1'
          }, {
            id: 8,
            label: 'Level two 3-2'
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    }
  };
</script>
```
:::

### ツリーノードのチェック

:::demo この例では、チェックされたノードを取得して設定する方法を示しています。どちらも、ノードとキーの2つのアプローチで行うことができます。キーアプローチの場合は `node-key` が必要です。
```html
<el-tree
  :data="data"
  show-checkbox
  default-expand-all
  node-key="id"
  ref="tree"
  highlight-current
  :props="defaultProps">
</el-tree>

<div class="buttons">
  <el-button @click="getCheckedNodes">get by node</el-button>
  <el-button @click="getCheckedKeys">get by key</el-button>
  <el-button @click="setCheckedNodes">set by node</el-button>
  <el-button @click="setCheckedKeys">set by key</el-button>
  <el-button @click="resetChecked">reset</el-button>
</div>

<script>
  export default {
    methods: {
      getCheckedNodes() {
        console.log(this.$refs.tree.getCheckedNodes());
      },
      getCheckedKeys() {
        console.log(this.$refs.tree.getCheckedKeys());
      },
      setCheckedNodes() {
        this.$refs.tree.setCheckedNodes([{
          id: 5,
          label: 'Level two 2-1'
        }, {
          id: 9,
          label: 'Level three 1-1-1'
        }]);
      },
      setCheckedKeys() {
        this.$refs.tree.setCheckedKeys([3]);
      },
      resetChecked() {
        this.$refs.tree.setCheckedKeys([]);
      }
    },

    data() {
      return {
        data: [{
          id: 1,
          label: 'Level one 1',
          children: [{
            id: 4,
            label: 'Level two 1-1',
            children: [{
              id: 9,
              label: 'Level three 1-1-1'
            }, {
              id: 10,
              label: 'Level three 1-1-2'
            }]
          }]
        }, {
          id: 2,
          label: 'Level one 2',
          children: [{
            id: 5,
            label: 'Level two 2-1'
          }, {
            id: 6,
            label: 'Level two 2-2'
          }]
        }, {
          id: 3,
          label: 'Level one 3',
          children: [{
            id: 7,
            label: 'Level two 3-1'
          }, {
            id: 8,
            label: 'Level two 3-2'
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    }
  };
</script>
```
:::

### カスタムノードの内容
ツリーノードの内容をカスタマイズできるので、好きなようにアイコンやボタンを追加することができます。

:::demo ツリーノードのテンプレートをカスタマイズするには、`render-content` とスコープ付きスロットの2つの方法があります。ツリーノードの内容を返すレンダー関数を割り当てるには、`render-content` を使用します。レンダリング関数の詳細については、Vueのドキュメントを参照してください。スコープされたスロットを使用したい場合は、スコープ内の `node` と `data` にアクセスできます。JSX 構文をサポートしていないため、`render-content` デモは jsfiddle で実行できないことに注意してください。実際のプロジェクトでは、関連する依存関係が正しく設定されていれば `render-content` は動作します。
```html

```
:::

### ツリーノードフィルタリング
ツリーノードはフィルタリング出来る。

:::demo ツリーインスタンスの `filter` メソッドを呼び出してツリーノードをフィルタリングします。そのパラメータはフィルタリングキーワードである。これが動作するためには `filter-node-method` が必要であり、その値がフィルタリングメソッドであることに注意すること。
```html
<el-input
  placeholder="Filter keyword"
  v-model="filterText">
</el-input>

<el-tree
  class="filter-tree"
  :data="data"
  :props="defaultProps"
  default-expand-all
  :filter-node-method="filterNode"
  ref="tree">
</el-tree>

<script>
  export default {
    watch: {
      filterText(val) {
        this.$refs.tree.filter(val);
      }
    },

    methods: {
      filterNode(value, data) {
        if (!value) return true;
        return data.label.indexOf(value) !== -1;
      }
    },

    data() {
      return {
        filterText: '',
        data: [{
          id: 1,
          label: 'Level one 1',
          children: [{
            id: 4,
            label: 'Level two 1-1',
            children: [{
              id: 9,
              label: 'Level three 1-1-1'
            }, {
              id: 10,
              label: 'Level three 1-1-2'
            }]
          }]
        }, {
          id: 2,
          label: 'Level one 2',
          children: [{
            id: 5,
            label: 'Level two 2-1'
          }, {
            id: 6,
            label: 'Level two 2-2'
          }]
        }, {
          id: 3,
          label: 'Level one 3',
          children: [{
            id: 7,
            label: 'Level two 3-1'
          }, {
            id: 8,
            label: 'Level two 3-2'
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    }
  };
</script>
```
:::

### アコーディオン

一度に展開できるのは同一レベル内の1つのノードのみです。

:::demo
```html
<el-tree
  :data="data"
  :props="defaultProps"
  accordion
  @node-click="handleNodeClick">
</el-tree>

<script>
  export default {
    data() {
      return {
        data: [{
          label: 'Level one 1',
          children: [{
            label: 'Level two 1-1',
            children: [{
              label: 'Level three 1-1-1'
            }]
          }]
        }, {
          label: 'Level one 2',
          children: [{
            label: 'Level two 2-1',
            children: [{
              label: 'Level three 2-1-1'
            }]
          }, {
            label: 'Level two 2-2',
            children: [{
              label: 'Level three 2-2-1'
            }]
          }]
        }, {
          label: 'Level one 3',
          children: [{
            label: 'Level two 3-1',
            children: [{
              label: 'Level three 3-1-1'
            }]
          }, {
            label: 'Level two 3-2',
            children: [{
              label: 'Level three 3-2-1'
            }]
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    },
    methods: {
      handleNodeClick(data) {
        console.log(data);
      }
    }
  };
</script>
```
:::

### ドラッグ可能

ツリーノードに `draggable` 属性を追加することで、ツリーノードをドラッグ＆ドロップすることができます。

:::demo
```html
<el-tree
  :data="data"
  node-key="id"
  default-expand-all
  @node-drag-start="handleDragStart"
  @node-drag-enter="handleDragEnter"
  @node-drag-leave="handleDragLeave"
  @node-drag-over="handleDragOver"
  @node-drag-end="handleDragEnd"
  @node-drop="handleDrop"
  draggable
  :allow-drop="allowDrop"
  :allow-drag="allowDrag">
</el-tree>

<script>
  export default {
    data() {
      return {
        data: [{
          label: 'Level one 1',
          children: [{
            label: 'Level two 1-1',
            children: [{
              label: 'Level three 1-1-1'
            }]
          }]
        }, {
          label: 'Level one 2',
          children: [{
            label: 'Level two 2-1',
            children: [{
              label: 'Level three 2-1-1'
            }]
          }, {
            label: 'Level two 2-2',
            children: [{
              label: 'Level three 2-2-1'
            }]
          }]
        }, {
          label: 'Level one 3',
          children: [{
            label: 'Level two 3-1',
            children: [{
              label: 'Level three 3-1-1'
            }]
          }, {
            label: 'Level two 3-2',
            children: [{
              label: 'Level three 3-2-1'
            }]
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    },
    methods: {
      handleDragStart(node, ev) {
        console.log('drag start', node);
      },
      handleDragEnter(draggingNode, dropNode, ev) {
        console.log('tree drag enter: ', dropNode.label);
      },
      handleDragLeave(draggingNode, dropNode, ev) {
        console.log('tree drag leave: ', dropNode.label);
      },
      handleDragOver(draggingNode, dropNode, ev) {
        console.log('tree drag over: ', dropNode.label);
      },
      handleDragEnd(draggingNode, dropNode, dropType, ev) {
        console.log('tree drag end: ', dropNode && dropNode.label, dropType);
      },
      handleDrop(draggingNode, dropNode, dropType, ev) {
        console.log('tree drop: ', dropNode.label, dropType);
      },
      allowDrop(draggingNode, dropNode, type) {
        if (dropNode.data.label === 'Level two 3-1') {
          return type !== 'inner';
        } else {
          return true;
        }
      },
      allowDrag(draggingNode) {
        return draggingNode.data.label.indexOf('Level three 3-1-1') === -1;
      }
    }
  };
</script>
```
:::

### 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-class            | custome tree node icon                                       | string                     | -    | -  |
| 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 | boolean, function(data, node) | —    | —    |
| isLeaf | specify whether the node is a leaf node, only works when lazy load is enabled | boolean, 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) the node's key to be highlighted. If `null`, cancel the currently highlighted node |
| setCurrentNode  | set highlighted node, only works when `node-key` is assigned | (node) the node to be highlighted |
| 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 |
| 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. |

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