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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?
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) */ } );
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