## DropdownMenu

### Install

``` javascript
import { DropdownMenu, DropdownItem } from 'vant';

Vue.use(DropdownMenu).use(DropdownItem);
```

### Usage

#### Basic Usage

```html
<van-dropdown-menu>
  <van-dropdown-item v-model="value1" :options="option1" />
  <van-dropdown-item v-model="value2" :options="option2" />
</van-dropdown-menu>
```

```js
export default {
  data() {
    return {
      value1: 0,
      value2: 'a',
      option1: [
        { text: 'Option1', value: 0 },
        { text: 'Option2', value: 1 },
        { text: 'Option3', value: 2 }
      ],
      option2: [
        { text: 'Option A', value: 'a' },
        { text: 'Option B', value: 'b' },
        { text: 'Option C', value: 'c' },
      ]
    }
  }
};
```

### Custom Content

```html
<van-dropdown-menu>
  <van-dropdown-item v-model="value" :options="option" />
  <van-dropdown-item title="Title" ref="item">
    <van-switch-cell v-model="switch1" title="Title" />
    <van-switch-cell v-model="switch2" title="Title" />
    <van-button block type="info" @click="onConfirm">Confirm</van-button>
  </van-dropdown-item>
</van-dropdown-menu>
```

```js
export default {
  data() {
    return {
      value: 0,
      switch1: false,
      switch2: false,
      option: [
        { text: 'Option1', value: 0 },
        { text: 'Option2', value: 1 },
        { text: 'Option3', value: 2 }
      ]
    }
  },

  methods: {
    onConfirm() {
      this.$refs.item.toggle();
    }
  }
};
```

### DropdownMenu Props

| Attribute | Description | Type | Default |
|------|------|------|------|------|
| active-color | Active color of title and option | `String` | `#1989fa` |
| z-index | z-index of menu item | `Number` | `10` |
| overlay | Whether to show overlay | `Boolean` | `true` |
| close-on-click-overlay | Whether to close when click overlay | `Boolean` | `true` |

### DropdownItem Props

| Attribute | Description | Type | Default |
|------|------|------|------|------|
| value | Value of current option，can use `v-model` | `String | Number` | - |
| title | Item title | `String` | Text of selected option |
| options | Options | `Array` | `[]` |

### DropdownItem Events

| Event | Description | Arguments |
|------|------|------|
| change | Triggered select option and value changed | value |

### DropdownItem Methods

Use ref to get DropdownItem instance and call instance methods

| Name | Attribute | Return value | Description |
|------|------|------|------|
| toggle | show: boolean | - | Toggle display |
