date: 2020-07-13 20:26
    title: [day95]Promise.all？

    Promise.all中任何一个Promise出现错误的时候都会执行reject，导致其它正常返回的数据也无法使用。你有什么解决办法么？

    1）在单个的catch中对失败的promise请求做处理
    2）把reject操作换成 resolve(new Error(“自定义的error”))
    3）引入Promise.allSettled

    1. const promises = [
    2.     fetch('/api1'),
    3.     fetch('/api2'),
    4.     fetch('/api3'),
    5.   ];
    7.   Promise.allSettled(promises).
    8.     then((results) => results.forEach((result) => console.log(result.status)));
    9.   // "fulfilled"

    4）安装第三方库 promise-transaction

    1. // 它是promise事物实现 不仅仅能处理错误还能回滚
    2.   import Transaction from 'promise-transaction';
    3. const t = new Transaction([
    4.   {
    5.     name: 'seed',
    6.     perform: () => Promise.resolve(3),
    7.     rollback: () => false,
    8.     retries: 1, // optionally you can define how many retries you like to run if initial attemp fails for this step
    9.   },
    10.   {
    11.     name: 'square',
    12.     perform: (context) => {
    13.       return Promise.resolve(context.data.seed * context.data.seed);
    14.     },
    15.     rollback: () => false,
    16.   },
    17. ]);
    19. return t.process().then((result) => {
    20.   console.log(result); // should be value of 9 = 3 x 3
    21. });