1         console.log("代码开始执行");
 2 
 3         setTimeout(() => {
 4           console.log("执行定时器");
 5         },0);
 6 
 7         let promise = new Promise((resolve,reject) =>{
 8             console.log("初始化promise状态");
 9             
10         });
11 
12         console.log(promise);
13 
14         console.log("代码执行结束");

 1     console.log("代码开始执行");
 2 
 3     setTimeout(() => {
 4       console.log("执行定时器1");
 5     }, 0);
 6 
 7     let promise = new Promise((resolve, reject) => {
 8       console.log("初始化promise状态");
 9       setTimeout(() => {
10         resolve();
11         console.log("resolve()执行");
12         // reject();
13         // console.log("reject()执行");
14       }, 1000);
15     });
16 
17     console.log(promise);
18 
19     console.log("代码执行结束");
20   
21     promise
22       .then(()=>{
23         console.log("resolve()执行为成功");
24         
25       },()=>{
26         console.log("reject()执行为失败");
27         
28       });

 1     let num = 0;
 2 
 3     function util() {
 4       num++;
 5       let promise = new Promise((resolve, reject) => {
 6         console.log("初始化promise状态");
 7         setTimeout(() => {
 8           resolve(`第${num}个异步方法执行成功`);
 9           console.log("resolve(msg)执行");
10           // reject("第一个异步方法执行失败");
11           // console.log("reject(msg)执行");
12         }, 1000);
13       });
14       
15       return promise;
16     }
17 
18     util()
19       .then((success) => {
20         console.log(success);
21 
22         if (success) {
23 
24           return util();    //第二个异步任务
25         }
26 
27       }, (failure) => {
28         console.log(failure);
29 
30       })
31     .then((success) =>{
32       console.log(success);
33     },(failure) =>{
34       console.log(failure);
35     });

 1     let num = 0;
 2 
 3     function util() {
 4       num++;
 5       let promise = new Promise((resolve, reject) => {
 6         console.log("初始化promise状态");
 7         setTimeout(() => {
 8           resolve(`第${num}个异步方法执行成功`);
 9           console.log("resolve(msg)执行");
10           // reject("第一个异步方法执行失败");
11           // console.log("reject(msg)执行");
12         }, 1000);
13       });
14       
15       return promise;
16     }
17 
18     util()
19       .then((success) => {
20         console.log(success);
21 
22       }, (failure) => {
23         console.log(failure);
24 
25       })
26     .then((success) =>{
27       console.log(success);
28       console.log(`第2个异步方法执行成功`);
29     },(failure) =>{
30       console.log(failure);
31     });

 1     let num = 0;
 2 
 3     function util() {
 4       num++;
 5       let promise = new Promise((resolve, reject) => {
 6         console.log("初始化promise状态");
 7         setTimeout(() => {
 8           // resolve(`第${num}个异步方法执行成功`);
 9           // console.log("resolve(msg)执行");
10           reject(`第${num}个异步方法执行失败`);
11           console.log("reject(msg)执行");
12         }, 1000);
13       });
14       
15       return promise;
16     }
17 
18     util()
19       .then((success) => {
20         console.log(success);
21 
22       }, (failure) => {
23         console.log(failure);
24 
25       })
26     .then((success) =>{
27       console.log(success);
28       console.log(`第2个异步方法执行成功`);
29     },(failure) =>{
30       console.log(failure);
31       console.log(`第2个异步方法执行失败`);
32     });

 1     let num = 0;
 2 
 3     function util() {
 4       num++;
 5       let promise = new Promise((resolve, reject) => {
 6         console.log("初始化promise状态");
 7         setTimeout(() => {
 8           // resolve(`第${num}个异步方法执行成功`);
 9           // console.log("resolve(msg)执行");
10           reject(`第${num}个异步方法执行失败`);
11           console.log("reject(msg)执行");
12         }, 1000);
13       });
14       
15       return promise;
16     }
17 
18     util()
19       .then((success) => {
20         console.log(success);
21 
22       }, (failure) => {
23         console.log(failure);
24 
25       })
26     .then((success) =>{
27       console.log(success);
28       console.log(`第2个异步方法执行成功`);
29     },(failure) =>{
30       console.log(failure);
31       console.log(`第2个异步方法执行失败`);
32     })
33     .then((success) =>{
34       console.log(success);
35       console.log(`第3个异步方法执行成功`);
36     },(failure) =>{
37       console.log(failure);
38       console.log(`第3个异步方法执行失败`);
39     });