es6提供的異步編程解決方案 值js中可看成一個特殊的函數，由function+*+函數名(){}構成 ``` function*gen(){ console.log("hello world") } let iterator=gen(); iterator.next();//調用next才輸出hello world！ ``` 由yield分割代碼，每調用一個next執行一個yield語句塊 ``` function*gen(){ console.log("a") yield "1"; console.log("b") yield "2"; console.log("c") yield "3"; console.log("d") yield "4"; } let iterator=gen(); iterator.next();//a iterator.next();//b iterator.next();//c iterator.next();//d iterator.next();//無輸出 function*gen(){ yield "1"; yield "2"; yield "3"; yield "4"; } for (let v of gen()) { console.log(v);//一次輸出1，2，3，4 } ``` 生成器參數 ``` function*gen(arg){ console.log(arg);//AAA } let iterator1=gen("AAA"); iterator1.next(); function*gen(){ let one=yield 111; console.log(one) let two=yield 222; console.log(two); let three=yield 333; console.log(three) } let iterator2=gen(); iterator2.next(); iterator2.next("BBB");//由one接收 iterator2.next("CCC");//由two接收 iterator2.next("DDD");//由three接收 ``` 實例： ``` //1s后控制臺輸出11，2s后輸出22，3s后輸出33 //更多輸出就嵌套更多，回調地獄 setTimeout(()=>{ console.log(11) setTimeout(()=>{ console.log(22) setTimeout(()=>{ console.log(33) },3000) },2000) },1000) //生成器實現解決回調地獄 function one(){ setTimeout(()=>{ console.log(11); iterator.next(); },1000) } function two(){ setTimeout(()=>{ console.log(22); iterator.next(); },2000) } function three(){ setTimeout(()=>{ console.log(33); iterator.next(); },3000) } function * gen(){ yield one(); yield two(); yield three(); } let iterator=gen(); iterator.next(); ``` ``` function getUsers(){ setTimeout(()=>{ let users="用戶數據"; iterator.next(users); },1000) } function getOrders(){ setTimeout(()=>{ let orders="用戶訂單"; iterator.next(orders); },1000) } function getGoods(){ setTimeout(()=>{ let goods="用戶商品"; iterator.next(goods); },1000) } function * gen(){ let users = yield getUsers(); console.log(users); let orders = yield getOrders(); console.log(orders); let goods = yield getGoods(); console.log(goods); } let iterator=gen(); iterator.next(); ```