callback - 通过计数器的方式实现多异步并发

通过最原始方式实现异步多并发

	let times 	= 3;
	let obj 	= {};	
	
	function out(obj){
		times--;
		if(times === 0){
			console.log(obj);
		}
	}


	setTimeout(()=>{
		obj['name'] = 'Yizhong';
		out(obj);
	}, 2000);
	
	setTimeout(()=>{
		obj['age'] = '33';
		out(obj);
	}, 3000);

	setTimeout(()=>{
		obj['address'] = 'Hefei';
		out(obj);
	}, 4000);

通过高阶函数(闭包)方式优化实现

function after(times, callback){
	
	return function(obj){
		if(--times === 0){
			callback(obj);
		}
	};
}

let obj = {};

let out = after(3, function(obj){
	console.log(obj);
});

setTimeout(()=>{
	obj['name'] = 'Yizhong';
	out(obj);
}, 2000);

setTimeout(()=>{
	obj['age'] = '33';
	out(obj);
}, 3000);

setTimeout(()=>{
	obj['address'] = 'Hefei';
	out(obj);
}, 4000);