If the options have a clear hierarchical structure, Cascader can be used to view and select them.
## Basic usage
There are two ways to expand child option items.
:::demo Assigning the `options` attribute to an array of options renders a Cascader. The `props.expandTrigger` attribute defines how child options are expanded.
cascader/basic
:::
## Disabled option
Disable an option by setting a `disabled` field in the option object.
:::demo In this example, the first item in `options` array has a `disabled: true` field, so it is disabled. By default, Cascader checks the `disabled` field in each option object; if you are using another field name to indicate whether an option is disabled, you can assign it in the `props.disabled` attribute (see the API table below for details). And of course, field name `value`, `label` and `children` can also be customized in the same way.
cascader/option-disabling
:::
## Clearable
Set `clearable` attribute for `el-cascader` and a clear icon will appear when selected and hovered
:::demo
cascader/clearable
:::
## Display only the last level
The input can display only the last level instead of all levels.
:::demo The `show-all-levels` attribute defines if all levels are displayed. If it is `false`, only the last level is displayed.
cascader/last-level
:::
## Multiple Selection
Set `props.multiple = true` to use multiple selection.
:::demo When using multiple selection, all selected tags will display by default, You can set `collapse-tags = true` to fold selected tags.
cascader/multiple-selection
:::
## Select any level of options
In single selection, only the leaf nodes can be checked, and in multiple selection, check parent nodes will lead to leaf nodes be checked eventually. When enable this feature, it can make parent and child nodes unlinked and you can select any level of options.
:::demo Set `props.checkStrictly = true` to make checked state of a node not affects its parent nodes and child nodes, and then you can select any level of options.
cascader/any-level
:::
## Dynamic loading
Dynamic load its child nodes when checked a node.
:::demo Set `lazy = true` to use dynamic loading, and you have to specify how to load the data source by `lazyload`. There are two parameters of `lazyload`,the first parameter `node` is the node currently clicked, and the `resolve` is a callback that indicate loading is finished which must invoke. To display the status of node more accurately, you can add a `leaf` field (can be modified by `props.leaf`) to indicate whether it is a leaf node. Otherwise, it will be inferred by if has any child nodes.
cascader/dynamic-loading
:::
## Filterable
Search and select options with a keyword.
:::demo Adding `filterable` to `el-cascader` enables filtering. Cascader will match nodes whose label or parent's label (according to `show-all-levels`) includes input keyword. Of course, you can customize search logic by `filter-method` which accepts a function, the first parameter is `node`, the second is `keyword`, and need return a boolean value indicating whether it hits.
cascader/filterable
:::
## Custom option content
You can customize the content of cascader node.
:::demo You can customize the content of cascader node by `scoped slot`. You'll have access to `node` and `data` in the scope, standing for the Node object and node data of the current node respectively。
cascader/custom-content
:::
## Cascader panel
`CascaderPanel` is the core component of `Cascader` which has various of features such as single selection, multiple selection, dynamic loading and so on.
:::demo Just like `el-cascader`, you can set alternative options by `options`, and enable other features by `props`, see the API form below for details.
| filterable | whether the options can be searched | boolean | — | — |
| filter-method | customize search logic, the first parameter is `node`, the second is `keyword`, and need return a boolean value indicating whether it hits. | function(node, keyword) | - | - |
| debounce | debounce delay when typing filter keyword, in milliseconds | number | — | 300 |
| before-filter | hook function before filtering with the value to be filtered as its parameter. If `false` is returned or a `Promise` is returned and then is rejected, filtering will be aborted | function(value) | — | — |
| popper-class | custom class name for Cascader's dropdown | string | — | — |
| popper-append-to-body | whether to append the popper menu to body. If the positioning of the popper is wrong, you can try to set this prop to false | boolean | - | true |
