利用观察者模式实现on、emit、off即事件绑定、事件触发、事件解除

function EventEmitter(){
    this.eventMap = new Map();
    this.arrFn = [];
    this.init();
}
$.extend(EventEmitter.prototype,{
    init(){
        //alert(1);
    },
    on(name,fn){
        if(!this.eventMap.get(name)){
            var newArray = new Array();
            newArray.push(fn);
            this.eventMap.set(name,newArray);
        }else{
            var oddArray = this.eventMap.get(name);
            oddArray.push(fn);
            this.eventMap.set(name,oddArray);
        }
    },
    emit(name,val){
        if(!this.eventMap.get(name)){
            return;
        }else{
            this.arrFn = this.eventMap.get(name);
            for(var i = 0,fn;fn = this.arrFn[i++];){
                fn(val);
            }
        }
        
    },
    off(name,fn){
        if(!fn){
            this.eventMap.delete(name);
        }else{
            this.arrFn = this.eventMap.get(name);
            var newArray = new Array();
            for(var i in this.arrFn){
                if(this.arrFn[i] != fn){
                    newArray.push(this.arrFn[i]);
                }
            }
            this.eventMap.set(name,newArray);
        }
    }
})
//测试
function fn(val){
    console.log("Tom" + val);
}
function fn1(val){
    console.log("Mary" + val);
}
function fn2(val){
    console.log("Jack" + val);
}
var emitter = new EventEmitter();
emitter.on("change",fn);
emitter.on("change",fn1);
emitter.on("change",fn2);
emitter.off("change",fn);
emitter.emit("change",123);