javascript – 在Promise中,使用catch和第二个参数之间的区别是什么？

参见英文答案 > When is .then(success,fail) considered an antipattern for promises?5个
这两个陈述之间究竟有什么区别？

funcThatReturnsAPromise()
  .then(() => { /* success */ })
  .catch(() => { /* fail */ });


funcThatReturnsAPromise()
  .then(() => { /* success */ },() => { /* fail */ });

解决方法

除了.catch(fn)是.then(null,fn)的快捷方式之外,你的例子中的区别在于

funcThatReturnsAPromise()
  .then(() => { /* success */ })
  .catch(() => { /* fail */ });

// is equivalent to

const p1 = funcThatReturnsAPromise()
const p2 = p1.then(() => { /* success */ })
const p3 = p2.catch(() => { /* 
   executed if p1 is rejected
   executed if p2 is rejected 
*/ })

而第二个是

funcThatReturnsAPromise()
  .then(() => { /* success */ },() => { /* fail */ });

// equivalent to

const p1 = funcThatReturnsAPromise()
const p2 = p1.then(
  () => { /* success */ },() => { /*
     executed if p1 is rejected
     (p2 will be actually resolved by the result of this function only when p1 is rejected)
  */ }
);