el-select 下拉框全选、多选的几种方式组件

<template>
  <el-select v-model="selectedOptions" multiple placeholder="请选择">
    <el-option
      v-for="item in options"
      :key="item.value"
      :label="item.label"
      :value="item.value">
    </el-option>
    <el-option :value="allOption.value" :label="allOption.label">
      <el-checkbox
        v-model="selectAll"
        @change="handleSelectAllChange">
        全选
      </el-checkbox>
    </el-option>
  </el-select>
</template>

<script>
export default {
  data() {
    return {
      selectedOptions: [],
      options: [
        { label: '选项1', value: 'option1' },
        { label: '选项2', value: 'option2' },
        { label: '选项3', value: 'option3' },
        // ...更多选项
      ],
      allOption: { label: '全选', value: 'all' },
      selectAll: false,
    };
  },
  watch: {
    selectedOptions(newSelection) {
      this.selectAll = newSelection.length === this.options.length;
    }
  },
  methods: {
    handleSelectAllChange(value) {
      if (value) {
        this.selectedOptions = this.options.map(item => item.value);
      } else {
        this.selectedOptions = [];
      }
    }
  }
};
</script>