Almost anything can be represented in a tree structure. Examples include directories, organization hierarchies, biological classifications, countries, etc. The `Tree` component is a way of representing the hierarchical relationship between these things. You can also expand, collapse, and select a treeNode within a `Tree`.
## API
### Tree props
| Property | Description | Type | Default | Version |
| blockNode | Whether treeNode fill remaining horizontal space | boolean | false | |
| checkable | Adds a `Checkbox` before the treeNodes | boolean | false | |
| checkedKeys(v-model) | (Controlled) Specifies the keys of the checked treeNodes (PS: When this specifies the key of a treeNode which is also a parent treeNode, all the children treeNodes of will be checked; and vice versa, when it specifies the key of a treeNode which is a child treeNode, its parent treeNode will also be checked. When `checkable` and `checkStrictly` is true, its object has `checked` and `halfChecked` property. Regardless of whether the child or parent treeNode is checked, they won't impact each other. | string\[] \| number\[] \| {checked: string\[] \| number\[], halfChecked: string\[] \| number\[]} | \[] | |
| checkStrictly | Check treeNode precisely; parent treeNode and children treeNodes are not associated | boolean | false | |
| defaultExpandAll | Whether to expand all treeNodes by default | boolean | false | |
| disabled | whether disabled the tree | bool | false | |
| draggable | Specifies whether this Tree is draggable (IE > 8) | boolean | false | |
| expandedKeys(v-model) | (Controlled) Specifies the keys of the expanded treeNodes | string\[] \| number\[] | \[] | |
| fieldNames | Replace the title,key and children fields in treeNode with the corresponding fields in treeData | object | { children:'children', title:'title', key:'key' } | 3.0.0 |
| filterTreeNode | Defines a function to filter (highlight) treeNodes. When the function returns `true`, the corresponding treeNode will be highlighted | function(node) | - | |
| selectable | whether can be selected | boolean | true | |
| selectedKeys(v-model) | (Controlled) Specifies the keys of the selected treeNodes | string\[] \| number\[] | - | |
| showIcon | Shows the icon before a TreeNode's title. There is no default style; you must set a custom style for it if set to `true` | boolean | false | |
| icon | customize icon. When you pass component, whose render will receive full TreeNode props as component props | slot\|slot-scope | - | |
| isLeaf | Determines if this is a leaf node(effective when `loadData` is specified) | boolean | false | |
| key | Used with (default)ExpandedKeys / (default)CheckedKeys / (default)SelectedKeys. P.S.: It must be unique in all of treeNodes of the tree! | string \| number | internal calculated position of treeNode | |
| selectable | Set whether the treeNode can be selected | boolean | true | |
