JavaScript Functions

Introduction to Functions

Functions are blocks of code designed to perform a particular task. They are executed when called They are essential for organizing and reusing logic.

Function Declaration

A basic function is declared using the function keyword:

function greet() {
  alert("Hello, world!");
}

greet(); // Call the function
            

Parameters and Arguments

You can pass values into functions using parameters:

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

greetUser("Alice");
            

Return Values

Functions can return values using the return keyword:

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

let result = add(5, 3); // 8
console.log(result);
            

Function Expressions

Functions can also be assigned to variables:

const multiply = function(x, y) {
  return x * y;
};

console.log(multiply(4, 5)); // 20
            

Arrow Functions (ES6)

Arrow functions offer a shorter syntax for writing functions:

const subtract = (a, b) => {
  return a - b;
};

console.log(subtract(10, 4)); // 6
            

Best Practices

• Use descriptive function names
• Keep functions short and focused on a single task
• Use arrow functions for concise logic (especially in callbacks)

Practice Task

Create a function that takes two numbers and returns their average:

function average(a, b) {
  return (a + b) / 2;
}

console.log("Average:", average(10, 20));