element/examples/docs/en-US/tree.md

Tree

Display a set of data with hierarchies.

Basic usage

Basic tree structure.

:::demo

<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>

:::

Selectable

Used for node selection.

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

<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>

:::

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.

<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>

:::

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.

<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>

:::

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.

<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>

:::

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.

<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>

:::

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.

<div class="custom-tree-container">
  <div class="block">
    <p>Using render-content</p>
    <el-tree
      :data="data"
      show-checkbox
      node-key="id"
      default-expand-all
      :expand-on-click-node="false"
      :render-content="renderContent">
    </el-tree>
  </div>
  <div class="block">
    <p>Using scoped slot</p>
    <el-tree
      :data="data"
      show-checkbox
      node-key="id"
      default-expand-all
      :expand-on-click-node="false">
      <span class="custom-tree-node" slot-scope="{ node, data }">
        <span>{{ node.label }}</span>
        <span>
          <el-button
            type="text"
            size="mini"
            @click="() => append(data)">
            Append
          </el-button>
          <el-button
            type="text"
            size="mini"
            @click="() => remove(node, data)">
            Delete
          </el-button>
        </span>
      </span>
    </el-tree>
  </div>
</div>

<script>
  let id = 1000;

  export default {
    data() {
      const 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'
        }]
      }];
      return {
        data: JSON.parse(JSON.stringify(data)),
        data: JSON.parse(JSON.stringify(data))
      }
    },

    methods: {
      append(data) {
        const newChild = { id: id++, label: 'testtest', children: [] };
        if (!data.children) {
          this.$set(data, 'children', []);
        }
        data.children.push(newChild);
      },

      remove(node, data) {
        const parent = node.parent;
        const children = parent.data.children || parent.data;
        const index = children.findIndex(d => d.id === data.id);
        children.splice(index, 1);
      },

      renderContent(h, { node, data, store }) {
        return (
          <span class="custom-tree-node">
            <span>{node.label}</span>
            <span>
              <el-button size="mini" type="text" on-click={ () => this.append(data) }>Append</el-button>
              <el-button size="mini" type="text" on-click={ () => this.remove(node, data) }>Delete</el-button>
            </span>
          </span>);
      }
    }
  };
</script>

<style>
  .custom-tree-node {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 14px;
    padding-right: 8px;
  }
</style>

:::

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.

<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>

:::

Accordion

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

:::demo

<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>

:::

Draggable

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

:::demo

<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 }