如何处理浏览器的断网情况？

其中insertAdjacentHTML是在标签节点的邻近位置插入，可以查阅：DOM进阶之insertAdjacentHTML

断网处理项目实战

可以基于vue，react封装出离线处理组件，在需要到的页面引入即可。

思路和效果

只要做到断网提醒+遮罩，上线提醒-遮罩即可。

• 
  
• 监听offline，断网给出提醒和遮罩：网络已断开，请检查网络连接。
  
• 监听online，连网给出提醒和遮罩：网络已连接。

<OfflineHandle
    offlineTitle = "断网处理标题"
    desc="断网处理描述"
    onlineTitle="连网提醒"
/>

Vue组件

<!--OfflineHandle.vue-->
<template>
  <div v-if="mask" class="offline-mask">
    <h2 class="offline-mask-title">{{ offlineTitle }}</h2>

    <p class="offline-mask-desc">{{ desc }}</p >
  </div>
</template>

<script>
export default {
  name: "offline-handle",
  props: {
    offlineTitle: {
      type: String,
      default: "网络已断开，请检查网络连接。",
    },
    onlineTitle: {
      type: String,
      default: "网络已连接",
    },
    desc: {
      type: String,
      default: "",
    },
    duration: {
      type: Number,
      default: 4.5,
    },
  },
  data() {
    return {
      mask: false,
    };
  },
  mounted() {
    window.addEventListener("offline", this.eventHandle);
    window.addEventListener("online", this.eventHandle);
    console.log(this.desc);
  },
  beforeDestroy() {
    window.removeEventListener("offline", this.eventHandle);
    window.removeEventListener("online", this.eventHandle);
  },
  methods: {
    eventHandle(event) {
      const type = event.type === "offline" ? "error" : "success";
      this.$Notice[type]({
        title: type === "error" ? this.offlineTitle : this.onlineTitle,
        desc: type === "error" ? this.desc : "",
        duration: this.duration,
      });
      setTimeout(() => {
        this.mask = event.type === "offline";
      }, 1500);
    },
  },
};
</script>

<style lang="css" scoped>
.offline-mask {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ccc;
  z-index: 9999;
  transition: position 2s;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}
.offline-mask-title {
  color: rgba(0, 0, 0, 0.8);
}
.offline-mask-desc {
  margin-top: 20px;
  color: red;
  font-weight: bold;
}
</style>

React组件

// offlineHandle.js
import React, { useState, useEffect } from "react";
import { notification } from "antd";
import "antd/dist/antd.css";
import "./index.css";

const OfflineHandle = (props) => {
  const {
    offlineTitle = "网络已断开，请检查网络连接。",
    onlineTitle = "网络已连接",
    desc,
    duration = 4.5
  } = props;
  const [mask, setMask] = useState(false);

  const eventHandler = (event) => {
    const type = event.type === "offline" ? "error" : "success";
    console.log(desc, "desc");
    openNotification({
      type,
      title: type === "error" ? offlineTitle : onlineTitle,
      desc: type === "error" ? desc : "",
      duration
    });
    setTimeout(() => {
      setMask(event.type === "offline");
    }, 1500);
  };

  const openNotification = ({ type, title, desc, duration }) => {
    notification[type]({
      message: title,
      description: desc,
      duration
    });
  };

  useEffect(() => {
    window.addEventListener("offline", eventHandler);
    window.addEventListener("online", eventHandler);
    return () => {
      window.removeEventListener("offline", eventHandler);
      window.removeEventListener("online", eventHandler);
    };
  }, []);

  const renderOfflineMask = () => {
    if (!mask) return null;
    return (
      <div className="offline-mask">
        <h2 className="offline-mask-title">{offlineTitle}</h2>

        <p className="offline-mask-desc">{desc}</p >
      </div>
    );
  };

  return <>{renderOfflineMask()}</>;
};

export default OfflineHandle;