发布订阅

<script type="text/javascript">
//发布 emit  订阅 on {女生失恋:['哭','购物','吃']}
function Girl(){
    this._events = {}
}
Girl.prototype.on = function(eventName,callback){
    if(this._events[eventName]){//不是第一次
        this._events[eventName].push(callback); //{失恋:[cry,eat,shopping]}
    }else{
        this._events[eventName] = [callback]; //{失恋:[cry]}
    }
};
Girl.prototype.emit = function(eventName,...args){//用剩余运算符[我，你，他]，在参数里叫剩余运算符
    //[].slice.call(arguments,1);都不理想
    //Array.from(arguments).slice(1);
    if(this._events[eventName]){
        //this._events[eventName].forEach(cb=>cb(...args));//在其他地方叫展开运算符
　　　　　　　　for(let i=0;i<args.length;i++){
　　　　　　　　　　this._events[eventName].forEach(item=>item(args[i]));
　　　　　　　　}

        //this._events[eventName].forEach(cb=>cb.apply(this,args));
    }
};
let girl = new Girl();
let cry = (who)=>{console.log(who + '哭');};
let shopping = (who)=>{console.log(who + '购物');};
let eat = (who)=>{console.log(who + '吃');};
girl.on('失恋',cry);//{失恋:[cry]}
girl.on('失恋',eat);//{失恋:[cry,eat]}
girl.on('失恋',shopping);//{失恋:[cry,eat,shopping]}

girl.emit('失恋','我','你');

//一对多
//{a:[fn,fn,fn]}
</script>

let events = {
    _events:[],
    on(fn){
        this._events.push(fn);
    },
    emit(data){
        this._events.forEach((event)=>{
            event(data);
        });
    }
};
let arr = [];

events.on((data)=>{
    arr.push(data);
    console.log(data)
});

events.on(()=>{
    if(arr.length === 2){
        console.log('老子不舔了')
    }
});

setTimeout(()=>{
    events.emit('第一次舔');
},1000);

setTimeout(()=>{
    events.emit('第二次舔');
},2000);