//generator处理异步，下一步用next，遇到return或者yied就会停止
{
//generator基本定义
let tell=function* (){
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());
}
{
let obj={};
obj[Symbol.iterator]=function*(){
yield 1;
yield 2;
yield 3;
}
for(let value of obj){
console.log('value',value)
}
}
{
//状态机
let state=function* (){
while(1){
yield 'A';
yield 'B';
yield 'C';
}
}
let status=state();
console.log(status.next());
console.log(status.next());
console.log(status.next());
console.log(status.next());
}
//和上面一样，但是需要安装插件
// {
// let state=async function(){
// while(1){
// await 'A';
// await 'B';
// await 'C';
// }
// }
// let status=state();
// console.log(status.next());
// console.log(status.next());
// console.log(status.next());
// console.log(status.next());
// }
{
//抽奖次数限制
let draw=function(count){
//具体逻辑
console.info(`剩余${count}次数`)
}
let residue=function* (count){
while(count>0){
count--;
yield draw(count);
}
}
let star=residue(5);
let btn=document.createElement('button');
btn.id='start';
btn.textContent='抽奖';
document.body.appendChild(btn);
document.getElementById('start').addEventListener('click',function(){
star.next();
},false)
}
{
//长轮询
let ajax=function*(){
yield new Promise(function(resolve,reject){
setTimeout(function(){
resolve({code:0})
},1000)
})
}
let pull=function(){
let generator=ajax();
let step=generator.next();
step.value.then(function(d){
if(d.code!=0){
setTimeout(function(){
console.log('wait');
pull()
},1000);
}else{
console.info(d);
}
})
}
pull();
}