Write a simple vue middleware, $emit, $on

foreword

Most of the students who have used vue know the use of $emit and $on. We just know how to use, and sometimes it's not enough. Now I will lead you to write a middleware that is simply similar to the empty instance of Vue.

Communication between non-parent-child components

The communication vue official website of non-parent-child components gives such a solution.
Sometimes communication is also required between two components that are not in a parent-child relationship. In simple scenarios, an empty Vue instance can be used as the event bus:

var bus = new Vue()
// 触发组件 A 中的事件
bus.$emit('id-selected', 1)
// 在组件 B 创建的钩子中监听事件
bus.$on('id-selected', function (id) {
  // ...
})

Simple example

Here is a very simple example

//工具
var myBus = (function() {
    var clienlist = {},
        addlisten, trigger, remove;
    /**
     * 增加订阅者
     * @key {String} 类型
     * @fn {Function} 回掉函数
     * */
    addlisten = function(key, fn) {
        if(!clienlist[key]) {
            clienlist[key] = [];
        }
        clienlist[key].push(fn);
    };
    /**
     * 发布消息
     * */
    trigger = function() {
        var key = [].shift.call(arguments), //取出消息类型
            fns = clienlist[key]; //取出该类型的对应的消息集合
        if(!fns || fns.length === 0) {
            return false;
        }
        for(var i = 0, fn; fn = fns[i++];) {
            fn.apply(this, arguments);
        }
    };
    /**
     * 删除订阅
     * @key {String} 类型
     * @fn {Function} 回掉函数
     * */
    remove = function(key, fn) {
        var fns = clienlist[key]; //取出该类型的对应的消息集合
        if(!fns) { //如果对应的key没有订阅直接返回
            return false;
        }
        if(!fn) { //如果没有传入具体的回掉，则表示需要取消所有订阅
            fns && (fns.length = 0);
        } else {
            for(var l = fns.length - 1; l >= 0; l--) { //遍历回掉函数列表
                if(fn === fns[l]) {
                    fns.splice(l, 1); //删除订阅者的回掉
                }
            }
        }
    };
    return {
        $on: addlisten,
        $emit: trigger,
        $off: remove
    }
})();
//组件一
Vue.component('vv-count', {
    props: ["count"],
    template: '<div>\
                 <span>{{count}}</span><button @click="handelClick" type="button">计算</button>\
               </div>',
    methods: {
        handelClick() {
            console.log('vv-count总计：', this.count);

            if(vue_bus){
                //触发发布--使用vue
                bus.$emit("vv_count", this.count,'这是使用vue的')
             }else{
                //触发发布--使用自己的
                myBus.$emit("vv_count", this.count,'这是自己写的')
             }
        }
    }
});
//组件二
Vue.component('vv-count1', {
    props: ["count"],
    template: '<div>\
                 <span>{{count}}</span><button @click="handelClick" type="button">计算</button>\
               </div>',
    methods: {
        handelClick() {
            console.log('vv-count1总计：', this.count);
             
             if(vue_bus){
                //触发发布
                bus.$emit("vv_count", this.count)
             }else{
                //触发发布
                myBus.$emit("vv_count", this.count)
             }
            
        }
    }
});

var vue_bus=true;// true：使用vue的事件总线，false:使用自己的事件总线


if(vue_bus){
    //中间件
    var bus = new Vue();
    //使用vue的事件总线--订阅
    bus.$on("vv_count", function() {
        console.log("使用bus发布的参数==", arguments);
    });
}else{
    //使用自己的事件总线--订阅
    myBus.$on("vv_count", function() {
        console.log("使用myBus发布的参数==", arguments);
    });
}


new Vue({
    el: "#app"
});

The above code can use vue_bus=true or false to switch each other to see the effect. as the picture shows:

If you want to see a more detailed explanation, please preview the publish-subscribe model or publish-subscribe model

Summarize

The publish and subscribe principle in vue is the same as the publish and subscribe principle written by oneself. I hope everyone can get the knowledge.

Reward channel -- I don't think there will be a reward.