vue2.x中事件总线EventBus的使用

一、使用方法

// eventBus.js
import Vue from "vue";
const EventBus = new Vue();
export default EventBus;

<template>
    <div>{{ message }}div>
template>

<script>
    import eventBus from './event-bus'
    export default {
        data() {
            return {
                message: '我是容器A的内容'
            }
        },
        mounted() {
            eventBus.$on("sendMessage", (msg) => {
                this.message = msg;
            })
        },
        destroyed() {
            eventBus.$off("sendMessage")
        }
    }
script>

<template>
    <button @click="sendToComponentA">点击button>
template>
<script>
    import eventBus from './event-bus'
    export default {
        methods: {
            sendToComponentA() {
                eventBus.$emit("sendMessage", "我来找容器A通信了")
            }
        }
    }
script>

二、手写实现 EventBus 原理

class EventBus {
    constructor() {
        this.callbacks = {}
    }
    $on(name, fn) {
        this.callbacks[name] = this.callbacks[name] || [];
        this.callbacks[name].push(fn);
        console.log('on callback', this.callbacks)
    }
    $emit(name, args) {
        if (this.callbacks[name]) {
            this.callbacks[name].forEach(cb => cb(args));
        }
        console.log('emit callback', this.callbacks);
    }
    $off(name) {
        if (this.callbacks[name]) delete this.callbacks[name];
        console.log('off callback', this.callbacks)
    }
}
export default new EventBus();