el-table实现全部选择和全部取消

其实非常简单，el-table自带的都有方法toggleAllSelection()和clearSelection()

具体代码如下：

<el-button type='success' @click='checkAll' size='small'>全选</el-button>
<el-button type='success' @click='cancelAll' size='small'>反选</el-button>

// 全选
checkAll() {
    this.$refs.table.toggleAllSelection()
}
// 反选
cancelAll() {
    this.$refs.table.clearSelection()
}