8. What are lambda expressions or arrow functions?

Lambda Expressions / Arrow Functions in JavaScript

In JavaScript, arrow functions (=>), also known as lambda expressions, provide a shorter and more concise way to write function expressions.

Syntax of an Arrow Function

javascript
CopyEdit
const functionName = (param1, param2) => expression;

Equivalent to:

javascript
CopyEdit
function functionName(param1, param2) {
  return expression;
}

Examples

1. Regular Function vs Arrow Function

javascript
CopyEdit
// Traditional function
function add(a, b) {
  return a + b;
}

// Arrow function
const add = (a, b) => a + b;

console.log(add(2, 3)); // 5

2. Arrow Function Without Parameters

javascript
CopyEdit
const greet = () => "Hello, World!";
console.log(greet()); // "Hello, World!"

3. Arrow Function With Single Parameter (Parentheses Optional)

javascript
CopyEdit
const square = x => x * x;
console.log(square(4)); // 16

4. Multi-line Arrow Function (With {} and return)

javascript
CopyEdit
const multiply = (a, b) => {
  let result = a * b;
  return result;
};

console.log(multiply(3, 4)); // 12

Key Differences Between Arrow Functions and Regular Functions

this in Arrow Functions

Arrow functions do not have their own this; they inherit it from the surrounding scope.

Example: this in Regular vs Arrow Functions

javascript
CopyEdit
function regularFunction() {
  console.log(this); // Refers to the caller object
}

const arrowFunction = () => {
  console.log(this); // Inherits `this` from the outer scope
};

regularFunction(); // `this` depends on how it's called
arrowFunction(); // `this` is from the surrounding scope

When to Use Arrow Functions?

✅ When using short, concise functions
✅ When lexical this behavior is desired (e.g., inside callbacks)
❌ Avoid when using methods inside objects or when needing arguments

Would you like more examples on how this behaves in different contexts? 🚀