javascript - 如何在async / await语法中拒绝？(How to reject in async/await syntax?)

Question

How can I reject a promise that returned by an async/await function?(如何拒绝async / await函数返回的promise？)

eg Originally(例如，最初) foo(id: string): Promise<A> { return new Promise((resolve, reject) => { someAsyncPromise().then((value)=>resolve(200)).catch((err)=>reject(400)) }); } Translate into async/await(转换为async / await) async foo(id: string): Promise<A> { try{ await someAsyncPromise(); return 200; } catch(error) {//here goes if someAsyncPromise() rejected} return 400; //this will result in a resolved promise. }); } So, how could I properly reject this promise in this case?(那么，在这种情况下，我怎么能正确地拒绝这个承诺呢？)   ask by Phoenix translate from so

Answer 1

Your best bet is to throw an Error wrapping the value, which results in a rejected promise with an Error wrapping the value:(你最好的办法是throw一个Error包装值，这会导致一个被拒绝的承诺，并包含一个Error值：)

} catch (error) { throw new Error(400); } You can also just throw the value, but then there's no stack trace information:(您也可以throw值，但是没有堆栈跟踪信息：) } catch (error) { throw 400; } Alternately, return a rejected promise with an Error wrapping the value:(或者，返回一个被拒绝的promise，其中包含一个Error ：) } catch (error) { return Promise.reject(new Error(400)); } (Or just return Promise.reject(400); , but again, then there's no context information.)(（或者只return Promise.reject(400);但是，再次，那么没有上下文信息。）) (In your case, as you're using TypeScript and foo 's retrn value is Promise<A> , you'd use return Promise.reject<A>(400 /*or error*/); )(（在你的情况下，当你使用TypeScript和foo的retrn值是Promise<A> ，你会使用return Promise.reject<A>(400 /*or error*/); ）) In an async / await situation, that last is probably a bit of a semantic mis-match, but it does work.(在async / await情况下，最后一个可能是语义不匹配，但确实有效。) If you throw an Error , that plays well with anything consuming your foo 's result with await syntax:(如果你抛出一个Error ，那么使用await语法消耗foo结果的任何东西都能很好地运行：) try { await foo(); } catch (error) { // Here, `error` would be an `Error` (with stack trace, etc.). // Whereas if you used `throw 400`, it would just be `400`. }