{

    // genertaor基本定义,next()一步步执行

    let tell=function* (){

        yield 'a';

        yield 'b';

        return 'c'

    };

    let k=tell();

    console.log(k.next()); //{value: "a", done: false}

    console.log(k.next()); //{value: "b", done: false}

    console.log(k.next()); //{value: "c", done: true}

    console.log(k.next());//{value: undefined, done: true}

}

// 应用场景，变量变化的实时存储

{

    let draw=function(count){

        // 具体抽奖逻辑

        console.info(`剩余${count}次`)

    }

    let residue=function *(count){

        while(count>){

            count--;

            yield draw(count);

        }

    }

    let star=residue();

    let btn=document.createElement("button");

    btn.id='star';

    btn.textContent='抽奖';

    document.body.appendChild(btn);

    document.getElementById('star').addEventListener("click",function(){

        star.next();

    },false)

}

{

    // 长轮询(服务端某个状态在变化，我们也需要实时去访问变化)

    let ajax=function* (){

        yield new Promise(function(resolve,reject){

            setTimeout(function(){

                resolve({code:})

            },);

        })

    }

    let pull=function(){

        let genertaor=ajax();

        let step=genertaor.next();

        step.value.then(function(d){

            if(d.code!=){

                setTimeout(function(){

                    console.info('wait');

                    pull()

                },);

            }else {

                console.log(d);

            }

        })

    }

    pull();

}