element dialog 封装到子组件中（ .sync修饰符与$emit(update:xxx)）

原理：https://blog.csdn.net/weixin_46995731/article/details/109765940

1、父组件调用

// .async: 对prop进行“双向绑定
<Dialog :visible.sync="dialogVisibleDemo" />

2、子组件

<template>
    <div class="dialog">
        <el-dialog title="提示" :visible.sync="dialogVisible" width="30%" @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>
</template>
<script>
export default {
    props: {
        visible: {
            type: Boolean,
            default: false,
        },
    },
    watch: {
        visible(value) {
            this.visible = value;
            this.dialogVisible = value;
        },
    },
    data: () => ({
        dialogVisible: false,
    }),
    methods: {
        handleClose() {
            // 改父组件通过props传递过来的变量
            this.$emit('update:visible', false);
        },
    },
};
</script>