Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript Asynchronous Programming with JavaScript Exploring Async/Await Error Handling with try...catch

Alex Weissman
Alex Weissman
720 Points
Posted by Alex Weissman
Alex Weissman
720 Points

Why do we need to catch and re-throw the error in getJSON?

In purely synchronous programming, there is no point in catching an exception just to re-throw it without doing anything else.

1 Answer

Steven Parker
Steven Parker
231,268 Points
Steven Parker
Steven Parker
231,268 Points

The instructor explains in the video, "The benefit of doing this is that any errors caught here will bubble up and be caught by try catch blocks or catch methods at the top level."

Then, later in the video a code example is provided to show this being used in practice.

JASON LEE
JASON LEE
17,352 Points

I still don't get it. Even without the try catch in the function getJSON(url), it will have the same behavior, where the error caught will bubble up and be caught by try catch block from the 'parent' function.

// Handle all fetch requests
async function getJSON(url) {
  try {
    const response = await fetch(url);
    return await response.json();
  } catch (error) {  
    throw error;  // <-- don't understand why catch and throw is necessary without any additional action/mod.
// As that would be the default behavior when an error occurs, is it not redundant?
  }
}
Steven Parker
Steven Parker
231,268 Points
Steven Parker
Steven Parker
231,268 Points

I see what you mean — why not just leave off the "try" completely. Now I'm also questioning the value of having one unless you were planning to add some code later between the "catch" and the "throw".