javascript - JavaScript承诺 - 拒绝与抛出(JavaScript Promises - reject vs. throw)

Question

I have read several articles on this subject, but it is still not clear to me if there is a difference between Promise.reject vs. throwing an error.(我已经阅读了几篇关于这个主题的文章，但我仍然不清楚Promise.reject与抛出错误之间是否存在差异。)

For example,(例如，) Using Promise.reject(使用Promise.reject) return asyncIsPermitted() .then(function(result) { if (result === true) { return true; } else { return Promise.reject(new PermissionDenied()); } }); Using throw(用投掷) return asyncIsPermitted() .then(function(result) { if (result === true) { return true; } else { throw new PermissionDenied(); } }); My preference is to use throw simply because it is shorter, but was wondering if there is any advantage of one over the other.(我倾向于使用throw只是因为它更短，但是想知道是否有一个优于另一个。)   ask by Naresh translate from so

Answer 1

There is no advantage of using one vs the other, but, there is a specific case where throw won't work.(使用一个与另一个没有任何优势，但是，有一个特定的情况， throw不起作用。)

However, those cases can be fixed.(但是，这些案件可以修复。) Any time you are inside of a promise callback, you can use throw .(每当你进入promise回调时，你都可以使用throw 。) However, if you're in any other asynchronous callback, you must use reject .(但是，如果您处于任何其他异步回调中，则必须使用reject 。) For example, this won't trigger the catch:(例如，这不会触发捕获：) new Promise(function() { setTimeout(function() { throw 'or nah'; // return Promise.reject('or nah'); also won't work }, 1000); }).catch(function(e) { console.log(e); // doesn't happen }); Instead you're left with an unresolved promise and an uncaught exception.(相反，你留下了未解决的承诺和未被捕获的异常。) That is a case where you would want to instead use reject .(在这种情况下，您可能希望改为使用reject 。) However, you could fix this by promisifying the timeout:(但是，你可以通过宣告超时来解决这个问题：) function timeout(duration) { // Thanks joews return new Promise(function(resolve) { setTimeout(resolve, duration); }); } timeout(1000).then(function() { throw 'worky!'; // return Promise.reject('worky'); also works }).catch(function(e) { console.log(e); // 'worky!' });