es6之generator

//generator

//基本用法
{
   // generator
    function* tell(){
        yield 'a';
        yield 'b';
        return 'c'
    };
    let k=tell();
    console.log(k.next());
    console.log(k.next());
    console.log(k.next());
    console.log(k.next());
}
//应用
{
    let obj={};
    obj[Symbol.iterator]=function *(){
       yield 1;
       yield 2;
       yield 3;
    }
    for(let item of obj){
        console.log(item)
    }
}

　//实例

    //实例
    let draw=function(count){
        //具体抽奖逻辑
        console.log(`剩余${count}次`);
    };

    let residue=function* (count){
        while(count>0){
            count--;
            yield  draw(count);
        }
    };

    let start=residue(5);
    let btn=document.createElement("button");
    btn.id="start";
    btn.textContent="抽奖";
    document.body.appendChild(btn);
    console.log(2222222222222);
    document.getElementById("start").addEventListener("click",function(){
        start.next();
    },false);

　长轮循

//长轮循
    //连续请求服务端接口，当服务端返回为0时，停止查询
    let ajax=function* (){
        yield new Promise(function(resolve, reject){
            //请求服务端的数据
            setTimeout(function(){
                resolve({code:0})
            },200)
        })
    }
    let pull=function(){
        let genertaor=ajax();
        let step=genertaor.next();
        step.value.then(function(d){
            if(d.code!=0){
                setTimeout(function(){
                    console.info("wait");
                    pull();
                },1000)
            }else{
                console.info(d);
            }
        })
    }
    pull();