Will it catch?🤯
#promise#async#errors
Omi

Omi @ompals

About: Software Engineer I am always curious, how developers make developers life easy! My favorite thing to do is, dive deep into a popular technology and get to know the "why" and "how" of it.

Location:
Surat, Gujarat, India
Joined:
Oct 27, 2020

Will it catch?🤯

Publish Date: Feb 22
3 2

Was just recovering from last Node.js blocking non-blocking stuff, I come to another JS injury called error-handling with promises.

This injury was again caused to me by not being able to distinguish between blocking and non-blocking code.

The below question is from javascript.info website.

What do you think? Will the .catch trigger? Explain your answer.

new Promise(function (resolve, reject) {
  setTimeout(() => {
    throw new Error("Whoops!");
  }, 1000);
}).catch(console.error);
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The hint: Look at the code like this:

new Promise(function (resolve, reject) 
// try {
{
  setTimeout(() => {
    throw new Error("Whoops!");
  }, 1000);
})
//} catch {
.catch(console.error);
// }
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Comment down your answer below!

Comments 2 total

  • Deep Gandhi
    Deep GandhiMar 23, 2025

    I thought the compiler would catch it, but when I ran it, the result differed from my expectation. Maybe it's because the error is in a different scope inside setTimeout? 🤔

    • Omi
      OmiMar 23, 2025

      The main thread execution looks something like this:

      new Promise(function (resolve, reject) 
try {
  // Register a setTimeout I/O
} catch(e) {
console.error(e.message);
}

// After 1 second
throw new Error("Whoops!");
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      The throw error statement will hang outside try...catch guards when defined in a callback of an async operation.

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