element-- el-table表头的全选按钮后加上“全选“

可以通过以下步骤在 el-table 表头的全选按钮后加上“全选”：

1. 在 el-table 组件中添加一个 slot，用于自定义表头内容：

<el-table :data="tableData" :row-key="row => row.id">
  <el-table-column type="selection" width="55">
    <template slot="header">
      <el-checkbox v-model="isAllSelected" @change="selectAll">{{selectAllText}}</el-checkbox>
    </template>
  </el-table-column>
  <el-table-column prop="name" label="Name"></el-table-column>
  <el-table-column prop="age" label="Age"></el-table-column>
</el-table>

2. 在 Vue 实例中添加以下代码：

data() {
  return {
    isAllSelected: false,
    selectAllText: '全选',
    tableData: [
      { id: 1, name: 'John', age: 20 },
      { id: 2, name: 'Jane', age: 25 },
      { id: 3, name: 'Bob', age: 30 }
    ]
  }
},
methods: {
  selectAll() {
    const isSelected = this.isAllSelected
    this.tableData.forEach(row => {
      row.$isSelected = isSelected
    })
  }
},
watch: {
  tableData: {
    handler() {
      const isAllSelected = this.tableData.every(row => row.$isSelected)
      this.isAllSelected = isAllSelected
    },
    deep: true
  }
}

3. 在 Vue 实例的 template 中修改 selectAllText 的值：

<template>
  <div>
    <el-table :data="tableData" :row-key="row => row.id">
      <el-table-column type="selection" width="55">
        <template slot="header">
          <el-checkbox v-model="isAllSelected" @change="selectAll">{{selectAllText}}</el-checkbox>
        </template>
      </el-table-column>
      <el-table-column prop="name" label="Name"></el-table-column>
      <el-table-column prop="age" label="Age"></el-table-column>
    </el-table>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isAllSelected: false,
      selectAllText: '全选',
      tableData: [
        { id: 1, name: 'John', age: 20 },
        { id: 2, name: 'Jane', age: 25 },
        { id: 3, name: 'Bob', age: 30 }
      ]
    }
  },
  methods: {
    selectAll() {
      const isSelected = this.isAllSelected
      this.tableData.forEach(row => {
        row.$isSelected = isSelected
      })
    }
  },
  watch: {
    tableData: {
      handler() {
        const isAllSelected = this.tableData.every(row => row.$isSelected)
        this.isAllSelected = isAllSelected
      },
      deep: true
    }
  }
}
</script>

这样就可以在 el-table 表头的全选按钮后添加“全选”了。