<cn>
#### 全选
在实现全选效果时，你可能会用到`indeterminate`属性
</cn>

<us>
#### Check all
The `indeterminate` property can help you to achieve a 'check all' effect.
</us>

```tpl
<template>
  <div>
    <div :style="{ borderBottom: '1px solid #E9E9E9' }">
      <a-checkbox :indeterminate="indeterminate" @change="onCheckAllChange" :checked="checkAll">
        Check all
      </a-checkbox>
    </div>
    <br />
    <a-checkbox-group :options="plainOptions" v-model="checkedList" @change="onChange" />
  </div>
</template>
<script>
  const plainOptions = ['Apple', 'Pear', 'Orange'];
  const defaultCheckedList = ['Apple', 'Orange'];
  export default {
    data() {
      return {
        checkedList: defaultCheckedList,
        indeterminate: true,
        checkAll: false,
        plainOptions,
      };
    },
    methods: {
      onChange(checkedList) {
        this.indeterminate = !!checkedList.length && checkedList.length < plainOptions.length;
        this.checkAll = checkedList.length === plainOptions.length;
      },
      onCheckAllChange(e) {
        Object.assign(this, {
          checkedList: e.target.checked ? plainOptions : [],
          indeterminate: false,
          checkAll: e.target.checked,
        });
      },
    },
  };
</script>
```