Explain JavaScript functions

JavaScript functions are blocks of code designed to perform particular tasks. A function is executed when something invokes it (calls it).

Syntax

function functionName(parameters) {
  // code to be executed
}

Example 1: Basic Function

function sayHello() {
  console.log("Hello, World!");
}

sayHello();

Output:

Hello, World!

Example 2: Function with Parameters

function greet(name) {
  console.log("Hello, " + name + "!");
}

greet("Alice");

Output:

Hello, Alice!

Example 3: Function with Return Value

function add(a, b) {
  return a + b;
}

let result = add(5, 3);
console.log(result);

Output:

8

Example 4: Anonymous Function

let multiply = function(a, b) {
  return a * b;
};

console.log(multiply(4, 7));

Output:

28

Example 5: Arrow Function

const divide = (a, b) => {
  return a / b;
};

console.log(divide(10, 2));

Output:

5

Example 6: Function with Default Parameters

function greet(name = "Guest") {
  console.log("Hello, " + name + "!");
}

greet();
greet("Bob");

Output:

Hello, Guest!
Hello, Bob!

Example 7: Immediately Invoked Function Expression (IIFE)

(function() {
  console.log("This function runs immediately!");
})();

Output:

This function runs immediately!

Example 8: Function as a Parameter

function repeat(operation, num) {
  for (let i = 0; i < num; i++) {
    operation();
  }
}

function sayHi() {
  console.log("Hi!");
}

repeat(sayHi, 3);

Output:

Hi!
Hi!
Hi!

These examples demonstrate different ways to define and use functions in JavaScript. Functions are fundamental to JavaScript programming, allowing for code reuse, modularity, and abstraction.