我们使用element-ui时会发现message-box消息提示是直接通过this.$message引用，而不是每次用的时候都先import然后注册组件。其实它的实现原理也很简单，主要就是使用了Vue.extend方法;接下来我们自己实现一个简单的message-box。

先看效果图：

1、message-box.vue

<template>
  <transition name="confirm-fade">
    <div class="confirm" v-show="showFlag">
      <div class="confirm-wrapper">
        <div class="confirm-content">
          <p class="text">{{title}}</p>
          <div class="operate" @click.stop>
            <div class="operate-btn left" @click="cancel">{{cancelBtnText}}</div>
            <div class="operate-btn" @click="confirm">{{confirmBtnText}}</div>
          </div>
        </div>
      </div>
    </div>
  </transition>
</template>


<script>
export default {
  data() {
    return {
      showFlag: false,
      title: "默认内容", 
      confirmBtnText: "确定",
      cancelBtnText: "取消"
    };
  },
  methods: {
    show() {
      this.showFlag = true
      return new Promise((resolve, reject) => {
        this.resolve = resolve
        this.reject = reject
      })
    },
    cancel() {
      this.reject('cancel')
      this.hide()
    },
    confirm() {
      this.resolve('confirm')
      this.hide()
    },
    hide() {
      this.showFlag = false
      document.body.removeChild(this.$el)
      this.$destroy()
    }
  }
};
</script>


<style scoped lang="scss">
.confirm {
  position: fixed;
  left: 0;
  right: 0;
  top: 0;
  bottom: 0;
  z-index: 998;
  background-color: rgba(0, 0, 0, 0.3);
  &.confirm-fade-enter-active {
    animation: confirm-fadein 0.3s;
    .confirm-content {
      animation: confirm-zoom 0.3s;
    }
  }
  .confirm-wrapper {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 999;
    .confirm-content {
      width: 270px;
      border-radius: 13px;
      background: #333;
      .text {
        padding: 19px 15px;
        line-height: 22px;
        text-align: center;
        font-size: 18px;
        color: rgba(255, 255, 255, 0.5);
      }
      .operate {
        display: flex;
        align-items: center;
        text-align: center;
        font-size: 18px;
        .operate-btn {
          flex: 1;
          line-height: 22px;
          padding: 10px 0;
          border-top: 1px solid rgba(0, 0, 0, 0.3);
          color: rgba(255, 255, 255, 0.3);
          &.left {
            border-right: 1px solid rgba(0, 0, 0, 0.3);
          }
        }
      }
    }
  }
}
@keyframes confirm-fadein {
  0% {opacity: 0;}
  100% {opacity: 1;}
}
@keyframes confirm-zoom {
  0% {transform: scale(0);}
  50% {transform: scale(1.1);}
  100% {transform: scale(1);}
}
</style>

2、message-box.js

import component from './index.vue'
function install (Vue) {
  Vue.prototype.$message = (options => {
    let Constructor = Vue.extend(component)
    let instance = new Constructor()
    instance.$mount()
    document.body.appendChild(instance.$el)
    Object.assign(instance, options)
    return instance.show()
  })
}


export default install

 3、main.js引入组件

import messageBox from './components/message-box/index.js'
Vue.use(messageBox)

4、代码中调用

this.$message({
  title: 'vue大法好!'
}).then(confirm => {
  console.log(confirm)  
}).catch(cancel => {
  console.log(cancel)
})

原文链接：https://huolihua.cn/#/article-detail/rsycy352oi800000

文章借鉴：https://juejin.cn/post/6844903946088103949