重学 MDN Web API 文档: Promise All In One

Promise

const myPromise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve("foo");
  }, 300);
});

// 错误用法 ❌
myPromise.then((res, err) => {
   console.log(`res =`, res);
   console.log(`err =`, err);
});
// res = foo
// err = undefined
// Promise {<fulfilled>: undefined}

const myPromise2 = new Promise((resolve, reject) => {
  setTimeout(() => {
    reject("bug");
  }, 0);
});

// 错误用法 ❌
myPromise2.then((res, err) => {
   console.log(`res =`, res);
   console.log(`err =`, err);
});
// ❌ Promise {<rejected>: 'bug'}
// Uncaught (in promise) bug

myPromise2.then((res) => {
   console.log(`res =`, res);
 }, (err) => {
   console.log(`err =`, err);
});
// err = bug
// Promise {<fulfilled>: undefined}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise#chained_promises

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标签：Web,MDN,log,err,res,API,Promise,console
From： https://www.cnblogs.com/xgqfrms/p/17145402.html