Debugging JavaScript Errors

Common JavaScript Errors

Examples include undefined is not a function, Uncaught ReferenceError, or syntax mistakes.

How to Fix:

1. Use Console Logs

Add console.log() to track variable values:

function calculateTotal(price, tax) {
  console.log("Price:", price, "Tax:", tax); // Debugging line
  return price * (1 + tax);
}
    

2. Check Syntax

Example of a syntax error (missing ;):

let name = "Alice"
alert(name) // Missing semicolon
    

Fixed code:

let name = "Alice";
alert(name);
    

3. Use Debugger Statement

Pause execution with debugger:

function init() {
  debugger; // Execution pauses here
  // ...code
}
    

4. Validate JSON

Use JSONLint to fix malformed JSON:

// Invalid JSON
{ "name": "Alice", "age": 30, }

// Valid JSON
{ "name": "Alice", "age": 30 }
    

Prevention Tips

• Use ESLint to catch errors early.
• Test code in a sandbox (e.g., CodePen).