element 下拉框加一个自定义选项

 <el-select v-model="value" clearable placeholder="请选择">
    <el-option
      v-for="item in options"
      :key="item.value"
      :label="item.name"
      :value="item.value">
    </el-option>
  </el-select>

data() {
  return {
     options: [{
         value: '1',
         name: '测试'
       }, {
         value: '2',
         name: '测试2'
       }, {
         value: '3',
         name: '测试3'
        }],
     value: ''
    }
 },
mounted(){
    this.options.unshift({value: "all", name: "全部"})
}