Lesson 2.1: Functions

Table of Contents

1. Introduction
2. Function Basics
3. Function Declaration
4. Function Parameters
5. Function Return
6. Using Comments

---

Introduction

In this lesson, you will learn about functions in JavaScript. Functions are like little code machines that take input, perform a task, and provide an output.

Why Should We Use Functions?

• Organization: Functions help break down complex code into smaller, manageable pieces.
• Reusability: Once you create a function, you can use it multiple times for the same task.
• Readability: Function names provide labels for the code's purpose.

Function Basics

Functions are structured like recipes or vending machines:

• Recipe: Takes ingredients (input), provides step-by-step instructions, and yields a completed dish (output).
• Vending Machine: Takes money and a selection (input), follows instructions, and dispenses a snack or drink (output).

Function Declaration

A function has the following syntax:

function functionName() {
  // Code goes here;
}

• Use the function keyword to declare a function.
• Give it a name followed by parentheses and curly braces.
• The function's body resides within the curly braces.

Function Parameters

You can add parameters to a function:

function squareNums(num) {
  console.log(num * num);
}

• Parameters act as placeholders for values used inside the function.

Function Return

A function can return a value:

function squareNumber(num) {
  let squared = num * num;
  return squared;
}

• The return statement stops the function and provides a value.
• The returned value can be a data type or variable.

Using Comments

Comments are essential for code readability and organization. They help you:

• Test specific code blocks.
• Assign tasks.
• Provide context for your code.

Comment Syntax:

• HTML: <!-- comment -->
• CSS (single-line): /* comment */
• CSS (multi-line): /* This is a multi-line comment */
• JavaScript (single-line): // comment
• JavaScript (multi-line): /* This is a multi-line comment */

Happy coding! 😊