Bits of .NET

🔒 Strict Mode = Fewer Bugs

JavaScript has quirks. Strict mode prevents common mistakes. Safer code, fewer bugs, better performance.

📝 Enabling Strict Mode

// Global strict mode
'use strict';

// Function-level strict mode
function myFunction() {
  'use strict';
  // Strict code here
}

// In modules (strict by default)
export default function() {
  // Already strict
}

// In classes (strict by default)
class MyClass {
  // Strict mode enabled

🎯 What Strict Mode Prevents

// ❌ Without strict mode (works, but bug)
x = 10;  // Global variable created (accidental)

// ✅ With strict mode (error)
'use strict';
x = 10;  // ReferenceError: x is not defined

// ❌ Without strict mode
function sum(a, a, c) { }  // Duplicate parameter

// ✅ With strict mode (error)
'use strict';
function sum(a, a, c) { }  // SyntaxError

// ❌ Without strict mode
delete Object.prototype;  // Silently fails

// ✅ With strict mode (error)
'use strict';
delete Object.prototype;  // TypeError

// ❌ Without strict mode
var obj = { get x() { return 1; } };
obj.x = 2;  // Silently fails

// ✅ With strict mode (error)
'use strict';
obj.x = 2;  // TypeError

// ❌ Without strict mode (works, security risk)
eval('var x = 10');

// ✅ With strict mode (eval is isolated)
'use strict';
eval('var x = 10');
console.log(x);  // ReferenceError (x is not defined)

💡 Benefits

• Prevents accidental globals
• Catches syntax errors earlier
• Disables dangerous features (with, eval)
• Better performance (optimized execution)
• Safer code