JavaScript Functions 🏗️

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JavaScript Functions 🏗️
Functions are reusable blocks of code that perform a specific task.

1️⃣ Defining Functions
Functions can be declared using function or expressed as variables.

✅ 1. Function Declaration

 

function greet() {

    console.log("Hello, world!");

}

greet(); // Output: Hello, world!

📌 Functions declared this way can be called before they are defined (hoisted).

✅ 2. Function Expression (Stored in a Variable)

JavaScript Functions const greet = function() {

    console.log("Hello, world!");

};

greet(); // Output: Hello, world!

📌 Function expressions are NOT hoisted (they must be defined before use).

✅ 3. Arrow Function (ES6+)

const greet = () => {

    console.log("Hello, world!");

};

greet(); // Output: Hello, world!

📌 Best for shorter, cleaner functions!

2️⃣ Function Parameters and Return Values
Functions can take inputs (parameters) and return outputs.

✅ 1. Function with Parameters

function greet(name) {

    console.log("Hello, " + name + "!");

}

greet("Alice"); // Output: Hello, Alice!

greet("Bob");   // Output: Hello, Bob!

📌 Parameters let you pass dynamic values.

✅ 2. Function with Multiple Parameters

function add(a, b) {

    console.log(a + b);

}

add(5, 3);  // Output: 8

add(10, 2); // Output: 12

✅ 3. Function with a Return Value

 

function multiply(a, b) {

    return a * b;

}

let result = multiply(4, 5);

console.log(result); // Output: 20

📌 return stops the function and sends back a value.

3️⃣ Default Parameters (ES6+)
If a parameter is not provided, JavaScript assigns a undefined value.
We can set default values to avoid issues.

 

function greet(name = "Guest") {

    console.log("Hello, " + name + "!");

}

greet();      // Output: Hello, Guest!

greet("Sam"); // Output: Hello, Sam!

4️⃣ Arrow Functions with Parameters
✅ Shorter Syntax for Simple Functions

 

const add = (a, b) => a + b;

console.log(add(3, 7)); // Output: 10

📌 No {} or return needed for one-line functions!

5️⃣ Function Scope (Local vs Global Variables)
Variables inside a function are local and can’t be accessed outside.

function example() {

    let x = 10; // Local variable

    console.log(x);

}

example(); // Output: 10

console.log(x); // ❌ Error: x is not defined

6️⃣ Summary
✅ Use functions to avoid repeating code.
✅ Use return to send back values.
✅ Use default parameters to handle missing values.
✅ Use arrow functions for cleaner code.

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    Date: 2025-03-29 00:00:00.000000