一种通过async/await实现函数同步执行的方式

 1 const testArr = [
 2   () => {
 3     return new Promise((resolve, reject) => {
 4       setTimeout(()=> {
 5         alert(1);
 6         resolve();
 7       }, 300);
 8     });
 9   },
10   () => {
11     return new Promise((resolve, reject) => {
12       setTimeout(()=> {
13         alert(2);
14         resolve();
15       }, 500);
16     });
17   },
18   () => {
19     return new Promise((resolve, reject) => {
20       setTimeout(()=> {
21         alert(3);
22         resolve();
23       }, 100);
24     });
25   }
26 ];
27 
28 async function iterate(arr) {
29   let index = 0;
30   while (index < arr.length - 1) {
31     await arr[index]();
32     index += 1;
33   }
34   return arr[index]();
35 }
36 
37 iterate(testArr);