ES6学习笔记七Generator、Decorators

Generator异步处理

{
    // 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

// 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>0){
            count--;
            yield draw(count);
        }
    }

    let star=residue(5);
    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)

{
    // 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:1})
            },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.log(d);
            }
        })
    }

    pull();
}

Decorator函数修饰符，通过修饰器修改类的行为