JavaScript

Debugging is the process of identifying and fixing errors or bugs in your code. In JavaScript, debugging helps ensure that your code works as expected and improves performance and stability.

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🎯 Why Debugging Matters

• Helps catch syntax and logic errors.
• Improves code quality.
• Saves time by isolating issues early.
• Crucial for understanding complex flows and behaviors in applications.

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🔍 Common Debugging Tools in JavaScript

1. console.log()

The most common and beginner-friendly way to debug.

let user = "Alice";
console.log("User name:", user);

Use this to:

• Check variable values
• Track the flow of execution
• Debug loops and function outputs

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2. Browser DevTools (Chrome, Firefox, Edge)

Open the Developer Tools:

• Chrome: Right-click → Inspect → Console / Sources
• Shortcut: Ctrl + Shift + I or F12

Key Panels:

• Console: Logs, errors, and interactive JS
• Sources: Debug code with breakpoints
• Network: Monitor API requests and responses
• Elements: Inspect and manipulate the DOM

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3. Breakpoints

Pause your code at a specific line using breakpoints in the Sources tab.

Steps:

1. Open DevTools → Sources
2. Click the line number to add a breakpoint
3. Reload the page or trigger the function
4. Use step controls (Step over, Step into, Step out) to walk through code

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4. debugger Statement

You can manually pause your code using the debugger keyword.

function calculateTotal(price, tax) {
  let total = price + tax;
  debugger; // Execution will pause here
  return total;
}

When the browser hits this line, it pauses just like a breakpoint.

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5. try...catch for Error Handling

Use this to catch and log errors without breaking your app.

try {
  let result = someUndefinedFunction();
} catch (error) {
  console.error("Caught an error:", error);
}

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6. Linting Tools (like ESLint)

• Detect syntax issues before running code.
• Can auto-fix or point out potential bugs.

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7. Error Stack Traces

When an error occurs, JavaScript prints a stack trace showing the file and line number of the error.

Uncaught ReferenceError: x is not defined
    at script.js:10

Use this information to jump directly to the error location.

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🧠 Tips for Effective Debugging

• Keep your console organized: use console.table() or console.group()
• Comment out sections to isolate issues
• Check browser compatibility issues
• Use typeof or Array.isArray() to confirm data types
• Use clear variable names to improve code readability

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🛠️ Advanced Debugging Tools

• React DevTools (for React apps)
• Redux DevTools (for state management debugging)
• VS Code Debugger (attach Chrome/Node for seamless debugging)

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✅ Summary

Technique	Use Case
console.log()	Quick checks
DevTools	Deep inspection & control
debugger	Manual pausing in code
Breakpoints	Pause and step through line-by-line
try...catch	Handle errors gracefully
Linting Tools	Prevent bugs early

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