Function Basics

Function Basics

A function is a block of reusable code that runs when you call it.

Declaring a function

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

Calling a function

sayHello();

Every time you call it, the code inside runs again.

Why use functions?

• Reuse code instead of writing it twice.
• Keep code organized and readable.
• Make changes in one place.
• Break big problems into small pieces.

Functions with names

Functions are declared with the function keyword, a name, parentheses, and a body:

function name() {
  // body
}

Function hoisting

Function declarations are hoisted, meaning you can call a function before it is declared in the file:

sayHello(); // works even though it is defined later
function sayHello() {
  console.log("Hello!");
}

TL;DR

• A function is reusable code defined with function name() { }.
• Call it with name().
• Functions keep code organized and reusable.
• Function declarations are hoisted.