错误不会在延迟方法中引发

Question

有人可以向我解释为什么我的第一个示例中没有抛出我的错误吗？当我使用process.nextTick() 时为什么会这样？

var deferred = require('deferred');

// This code does not work. 
// Error seems to never been thrown and script kind of freeze without saying anything.
deferred.resolve().then(function(){
    console.log('deferred resolved');
    throw new Error('Synchronous error thrown in deferred.then()');
});

// This code does work. 
// I just embedded the throw in the process.nextTick() method.
deferred.resolve().then(function(){
    console.log('deferred resolved');
    process.nextTick(function(){
        throw new Error('Synchronous error thrown in deferred.then()');
    });
});

为什么我需要等待 nextTick 在then() 内抛出错误...

任何解释将不胜感激。 谢谢

我看过这篇文章 (No errors thrown/displayed when in a deferred callback)。但它只给出了一半的答案......

Answer 1

在你的情况下，deferred 的行为在我看来是合理的。

在第二种情况下，我认为deferred 没有办法捕获nextTick 回调中抛出的错误。于是报错了。

在第一种情况下，deferred 捕获它并认为导致的承诺处于失败状态。 deferred 文档指出，如果你希望它有效地抛出一个将 Promise 推入失败状态的错误，你必须调用 done

deferred.resolve().then(function(){
  console.log('deferred resolved');
  throw new Error('Synchronous error thrown in deferred.then()');
}).done();

有关文档，请参阅 https://github.com/medikoo/deferred#ending-chain