Errors in JavaScript

Errors in JavaScript

Errors happen when something goes wrong in your code. JavaScript reports them so you can fix them.

Common error types

• SyntaxError: you wrote something JavaScript cannot understand.
• ReferenceError: you used a variable that does not exist.
• TypeError: you used a value the wrong way (like calling a number as a function).
• RangeError: a number is outside the allowed range.
• Error: a generic error.

Example ReferenceError

console.log(missingVariable);
// ReferenceError: missingVariable is not defined

Example TypeError

let n = 5;
n.toUpperCase();
// TypeError: n.toUpperCase is not a function

Errors stop the program

When an unhandled error happens, the script stops running at that point.

Reading an error

Errors usually include:

• The error type.
• A message explaining the problem.
• A stack trace showing where it happened.

The Error object

You can create errors yourself:

throw new Error("Something went wrong");

TL;DR

• Syntax, Reference, and TypeError are common errors.
• Errors stop the script unless handled.
• Errors include a type, message, and stack trace.
• throw new Error(...) creates errors.