A pen test from Xunlei front end

Implement an EventEmitter class, and implement the following methods:

1.emitter.on(name,fn) / / subscribe to the name event. The listening function is fn. You can subscribe multiple times

2.emitter.once(name,fn) / / the function is similar to on, but the listening function is one-time, which is automatically removed after triggering

3. Emit. Emit (name, data1, data2,..., datan) / / publish the name event. All the listening functions subscribed to the event are triggered. data1,...,datan are passed to the listening functions as parameters. If there are multiple functions, they are executed in order

4.emitter.remove(name,fn) / / remove the listening function fn of the name event

Code implementation:

//Publish and subscribe mode
	function EventEmitter(){
		//Cache list, store subscriber list
		var list = [];
		var instance;
		//Subscription event name,type = 0 for permanent subscription = 1 for primary subscription
		var on = function(name,fn,type = 0){
			//Determine whether the event has been subscribed
			if(!list[name]){
				list[name] = [];
			}
			list[name].push([fn,type]);//Listening function inserts the event list
		};
		//Delete subscription once triggered
		var once = function(name,fn,type = 1){
			on(name,fn,type);
		};
		//Release
		var emit = function(name){
			var fns = list[name];//Take out event
			//Get parameter list
			var args = [].slice.call(arguments,1);
			//Judge whether the listening function exists
			if (!fns || fns.length == 0) {
				return;
			}
			for(var i =0;i<fns.length,fn = fns[i++];){
				fn[0].apply(this,args);
				if(fn[1] == 1){
					remove(name,fn[0],1);
				}
			}
		};
		//Delete event
		var remove = function(name,fn,type = 0){
			if(!name){
				return;
			}
			var fns = list[name];
			//No listening function passed in, cancel all
			if(!fn){
				list[name] = [];
			}else{
				for(var i =0;i<fns.length,fn1 = fns[i];i++){
					//Find the corresponding function and delete it
					if(fn === fn1[0]&&type ===fn1[1]){
						fns.splice(i,1);
					}
				}
			}
		};
		return {
			on:on,
			once:once,
			emit:emit,
			remove,remove
		}
	}
	var emitter = new EventEmitter();
	var log = console.log;
	emitter.on('someTask',log);
	emitter.emit('someTask',1);//1
	emitter.emit('someTask',1,2);//1,2
	emitter.once('someTask',log);
	emitter.emit('someTask',1);//1
	emitter.emit('onceTask',1);//No output
	emitter.remove('someTask',log);
	emitter.emit('someTask',1);//No output