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. In the following example, data for each layer is acquired after being clicked. If there is no child data, the expanding icon will disappear.

::: demo

<el-tree
  :data="regions"
  :props="props"
  :load="loadNode"
  lazy
  show-checkbox
  @check-change="handleCheckChange">
</el-tree>

<script>
  export default {
    data() {
      return {
        regions: [{
          'name': 'region1'
        }, {
          'name': 'region2'
        }],
        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>

:::

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>

:::

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	—	—
load	method for loading subtree data	function(node, resolve)	—	—
render-content	render function for tree node	Function(h, { node }	—	—
highlight-current	whether current node is highlighted	boolean	—	false
current-node-key	key of current node, a set only prop	string, number	—	—
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.	—	true
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	—	—
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

props

Attribute	Description	Type	Accepted Values	Default
label	specify which key of node object is used as the node's label	string	—	—
children	specify which key of node object is used as the node's subtree	string	—	—

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
getCheckedNodes	If the node can be selected (show-checkbox is true), it returns the currently selected array of nodes	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.
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 true. 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 true. 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.

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
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
current-change	triggers when current node changes	two parameters: node object corresponding to the current node, node property of TreeNode
node-open	triggers when current node open	three parameters: node object corresponding to the node opened, node property of TreeNode, TreeNode itself
node-close	triggers when current node close	three parameters: node object corresponding to the node closed, node property of TreeNode, TreeNode itself