Day 9: Errors

Lesson 2: Catch()

The catch block of the try/catch structure can also take an argument that receives the thrown error. Here's the previous example expanded:

<h1>Hello World<h1>

try {
    throw new Error("Something went wrong");
} catch(error) {
  console.log("Whoops, looks like we caught an error: ", error.message);
}

By accessing the message we can see what error was thrown, then assuming we (or more likely, another developer) used a sensible error message we can investigate and fix it.

If the error wasn't that helpful then you can get the stack property as well to see if it can tell you where the error occurred. It won't be all that helpful here but go ahead and change the .message to .stack above to see where the error was thrown.

Writing good error messages is an art that takes time to develop so start practicing now when you find yourself writing error messages to help you in the future.

Something important to know is that if an error is thrown in the try, no code after the throw will be run in the try block.

Heres an example

<h1>Hello World<h1>

try {
    console.log("Hello ...");
    throw new Error("Something went wrong");
    console.log("World");
} catch(error) {
  console.log("Whoops, looks like we caught an error: ", error.message)
}

See how the Hello ... is logged but World isn't?

That's because after an error has happen it's assumed that nothing in the try block after that point is safe to run, so it's skipped and we go to the catch block to deal with the error.