Generator

生成器对象是由一个 generator function 返回的,并且它符合可迭代协议和迭代器协议。

    <script>
        function *go(){
            console.log("a");
            return 2;
        }
        /* done表示generate函数是否执行完毕,value是generate函数的返回值 */
        var obj = go();
        /* 
        1.*
        2.next()
        3. obj.next()  value,done
         */
        console.log(obj.next())
    </script>

generator函数遇到yield关键字 函数会暂停 yield将函数切割了
next( )方法会返回一个对象

        <script>
        function *gen(x){
            yield x+2;
            yield 7;
            return x;
        }
        /* generator函数遇到yield关键字 函数会暂停 yield将函数切割了
        next()方法会返回一个对象
         */
        var g = gen(3);
        console.log(g.next())//{value: 5, done: false}
        console.log(g.next()) //{value:3,done:true}
        console.log(g.next())
    </script>

    <script>
        function *go(x){
            var y = yield x+2;
            console.log(y)
            var z =  yield y+10;
            console.log(z);
            return 4;

        }
        var obj = go(3);
        console.log(obj.next())
        console.log(obj.next(7))
        console.log(obj.next(8))
    </script>

co

co = generator + promise

        <script src="https://cdn.bootcss.com/co/4.1.0/index.js"></script>
    <script>
       async  function go(x){
            return x;
        }
        co(function *(){
            var data = yield go(3);
            console.log(data)
            var y = yield go(4);
            console.log(y)
        })
    </script>

generator-http

        <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.js"></script>
    <script>
        var baseUrl = "http://localhost:3000/"
        function http(url){
            return $.ajax({
                url:baseUrl+url,
                dataType:"json"
            })
        }
        function *getData(){
            var id = yield http("top/playlist");
            console.log(id);
            yield http(`playlist/detail?id=${id}`);
        }
        var res  = getData();
       res.next().value.then(data=>{
           var {id,name} = data.playlists[0];
           res.next(id).value.then(res=>{
               console.log(res)
           })
       })
    </script>

co-http

        <script src="https://cdn.bootcss.com/co/4.1.0/index.js"></script>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.js"></script>
    <script>
        var baseUrl = "http://localhost:3000/"
        function http(url) {
            return $.ajax({
                url: baseUrl + url,
                dataType: "json"
            })
        }
        co(function *(){
            const data  = yield http("top/playlist");
            var {id,name} = data.playlists[0];
            const detail = yield http(`playlist/detail?id=${id}`)
            console.log(detail)
        })
    </script>

iterator

<script>
     function generator(arr){
         var nextIndex = 0;
         return {
             next:()=>{
                 if(nextIndex<arr.length){
                     return {value:arr[nextIndex++],done:false}
                 }else{
                     return {done:true}
                 }
             }
         }
     }
     var arr = ["起床",'吃中饭','睡觉'];
     var obj = generator(arr);
     console.log(obj.next());
     console.log(obj.next());
     console.log(obj.next());
     console.log(obj.next());
    </script>