SOURCE

var Main = {
    data() {
      return {
        dialogVisible: false
      };
    },
    methods: {
      handleClose(done) {
        this.$confirm('确认关闭？')
          .then(_ => {
            done();
          })
          .catch(_ => {});
      }
    }
  };
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')

<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/element-ui@1.4.1/lib/index.js"></script>
<div id="app">
<el-button type="text" @click="dialogVisible = true">点击打开 Dialog</el-button>

<el-dialog title="提示" :visible.sync="dialogVisible" size="tiny" :before-close="handleClose">
  <span>这是一段信息</span>
  <span slot="footer" class="dialog-footer">
    <el-button @click="dialogVisible = false">取 消</el-button>
    <el-button type="primary" @click="dialogVisible = false">确 定</el-button>
  </span>
</el-dialog>
</div>

@import url("//unpkg.com/element-ui@1.4.1/lib/theme-default/index.css");