Errors

Errors are a normal part of programming. Understanding them helps you debug faster.

Common Error Types

SyntaxError

Invalid JavaScript syntax — code can't even be parsed.

// SyntaxError: Unexpected token
console.log('hello'
// Missing closing parenthesis

ReferenceError

Accessing a variable that doesn't exist.

console.log(myUndefinedVar)
// ReferenceError: myUndefinedVar is not defined

TypeError

Performing an operation on the wrong type.

null.property
// TypeError: Cannot read properties of null

Reading Error Messages

Error messages have three key parts:

1. Error type — what category of error
2. Message — what went wrong
3. Stack trace — where it happened (file name + line number)