Promise,yield,异步回调

function showHint(str){
	return new Promise(function(reslove, reject){
		var xmlhttp;
		xmlhttp=new XMLHttpRequest();
		xmlhttp.onreadystatechange=function(){
			if (xmlhttp.readyState==4 && xmlhttp.status==200){
				reslove();
			}
		}
		xmlhttp.open("GET","http://d.alipay.net/xyebzdzr/serivce.htm",true);
		xmlhttp.send();
	})
	
}


//两个ajax 连续调用
//showHint().then(showHint).then(function(){console.log(2)});

//进一步封装 个个模块解耦

function showHint(){
	return new Promise(function(reslove, reject){
		var xmlhttp;
		xmlhttp=new XMLHttpRequest();
		xmlhttp.onreadystatechange=function(){
			if (xmlhttp.readyState==4 && xmlhttp.status==200){
				reslove(xmlhttp.statusText);
			}
		}
		xmlhttp.open("GET","http://d.alipay.net/xyebzdzr/serivce.htm",true);
		xmlhttp.send();
	})
	
}

var request = {
	a : function(){
		return showHint().then(function(val){return val});
	},
	b : function(){
		return showHint().then(function(val){return val});
	}
}

//两个ajax 同时发起请求 但必须满足两个都完成 才触发


function main(){
	return Promise.all([request.a(), request.b()]);
}

/*main().then(function(value){
	console.log(value);
})*/

//yield 加入战场

var requests = {
	a : function(){
		return showHint().then(function(val){return val});
	},
	b : function(){
		return showHint().then(function(val){return val});
	}
}


function* run(){
	yield requests.a();
	yield requests.b();
}


function iterator(g){
	var it = g();
		
	 void function () {
	 	var arg = arguments;
    	var curr = it.next();
        
        if(curr.done) {
            return ;
        }
        if(curr.value instanceof Promise) {
            curr.value.then(function(val){
            	console.log(val);
            	arg.callee();
            });
        } else {
        	arguments.callee();
        }
    }();
}
iterator(run)