Variables: Your Data Containers 📦

Why this matters: almost everything you do in code depends on naming and storing values. Clear, well-chosen variables make code readable, maintainable, and easy to change.

Variables are named boxes that hold values you want to reuse or change later.

Why Do We Need Variables?

• To avoid repeating the same literal value everywhere
• To make code easy to update in one place
• To store results of calculations for later steps

Imagine you have a labeled box where you can store things. In programming, those boxes are variables.

// Without variables (bad)
console.log("Welcome, Alex!");
console.log("Alex, you have 5 messages");
console.log("Goodbye, Alex!");

// With variables (good!)
let name = "Alex";
console.log("Welcome, " + name + "!");
console.log(name + ", you have 5 messages");
console.log("Goodbye, " + name + "!");

Now if you want to change "Alex" to "Sarah", you only change ONE line!

Creating a Variable

let name = "Sarah";
let age = 25;
let isStudent = true;

Breaking It Down

let name = "Sarah";
│    │       │
│    │       └── The value you're storing
│    └── The name you give your box (choose any name!)
└── "let" means "create a new variable"

Using Variables

Once created, just use the name (no quotes!):

let city = "London";
console.log(city);  // Shows: London
console.log("I live in " + city);  // Shows: I live in London

Variable Naming Rules

✅ Good names: userName, totalPrice, isLoggedIn ❌ Bad names: 1stPlace (can't start with number), user name (no spaces)

Your Turn!

Create a variable called city that stores the text "London"