JavaScript

Chapter 2 — JS Variables & Operators

📚 Chapter Overview

Before making a page dynamic, you must understand how JavaScript stores and manipulates data. In this chapter, you will learn the difference between let, const, and var, and how to perform calculations.

Learning Objectives:

2.1 Variables (let, const, var)

Part 1 — Definition

Variables are containers for storing data values. Modern JavaScript uses let for variables that can change and const for values that stay the same. var is an older way and is generally avoided in modern development.

Part 2 — Syntax

let score = 0;
const pi = 3.14;
var name = "John"; // Avoid in modern JS

Part 3 — Example

Problem: Keep track of a user's login status.

script.js 
const userName = "Alice";
let isLoggedIn = false;

// After login
isLoggedIn = true;
console.log(userName + " is logged in: " + isLoggedIn);

Part 4 — Video

Video: Coming Soon

2.2 Arithmetic and Template Literals

Part 1 — Definition

JavaScript supports standard math operators (+, -, *, /). Template Literals (using backticks ``) allow you to embed variables directly into strings using ${variable}, which is much cleaner than string concatenation.

Part 2 — Syntax

let total = a + b;
console.log(`The sum is ${total}`);

Part 3 — Example

Problem: Calculate the total price including tax.

script.js 
let price = 100;
let tax = 0.05;
let finalPrice = price + (price * tax);
console.log(`Total Price: $${finalPrice}`);

Output: Total Price: $105

Part 4 — Video

Video: Coming Soon

🏆 Chapter Challenge

Challenge Objective

Build a "Simple BMI Calculator" using JavaScript variables and math.

Requirements

Step-by-Step Process

  1. Use let for weight and height.
  2. Apply the math formula.
  3. Output the message: "Your BMI is [value]".

Expected Deliverables

Solve in Editor