需求:promise执行买菜作饭过程

1.买菜
2.洗菜
3.作饭
4.吃饭 html
 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>Document</title>
 8 </head>
 9 <body>
10     <h2>需求:promise执行买菜作饭过程</h2>   <br>
11     1.买菜  <br>
12     2.洗菜  <br>
13     3.作饭  <br>
14     4.吃饭  <br>
15 </body>
16     <script>
17         let flag =1; 18         function step1(resolve,reject){ 19            console.log("准备去买菜"); 20            if(flag==1){ 21              resolve("买好了") 22            }else{ 23              reject("没菜了") 24  } 25  } 26         
27         function step2(resolve,reject){ 28            console.log("洗菜"); 29            if(flag==1){ 30              resolve("洗好了"); 31            }else{ 32              reject("没水"); 33  } 34  } 35         function step3(resolve,reject){ 36            console.log("开始作饭"); 37            if(flag==1){ 38              resolve("作好了"); 39            }else{ 40              reject("煤气没了"); 41  } 42  } 43         function step4(resolve,reject){ 44            console.log("准备吃饭"); 45            if(flag==1){ 46              resolve("真好吃"); 47            }else{ 48              reject("真难吃"); 49  } 50  } 51         function step5(resolve,reject){ 52            console.log("剪刀石头布洗碗"); 53            if(flag==0){ 54              resolve("女友洗"); 55            }else{ 56              reject("不洗"); 57  } 58  } 59         new Promise(step1).then((val1)=>{ 60  console.log(val1); 61            return new Promise(step2) 62         }).then((val2)=>{ 63  console.log(val2); 64            return new Promise(step3) 65         }).then((val3)=>{ 66  console.log(val3) 67            return new Promise(step4) 68         }).then((val4)=>{ 69  console.log(val4) 70            return new Promise(step5) 71         }).then((val5)=>{ 72  console.log(val5) 73  }) 74     </script>
75 </html>