JavaScript Tutorial - Variables & Data Types
📦 Variables - Data Store Karo
🌟 Real Life Analogy:
Variable = Storage box
📦 Box hai → Variable
🏷️ Box ka label → Variable name
📝 Box mein rakhi cheez → Value
Example: let age = 25;
"age" naam ka box hai, usmein "25" rakha hai
🎯 Variable Declaration
| Keyword | Meaning | Can Change? | When to Use |
|---|---|---|---|
let | Modern way | ✅ Yes | Normal variables |
const | Constant | ❌ No | Fixed values (PI, config) |
var | Old way | ✅ Yes | ❌ Avoid (outdated) |
📊 Data Types
Common Types
| Type | Example | Real Life |
|---|---|---|
| Number | 25, 3.14, -10 | Age, price, temperature |
| String | "Hello", 'World' | Name, email, message |
| Boolean | true, false | Logged in? Yes/No |
| Array | [1, 2, 3] | Shopping list |
| Object | {name: "Rohan"} | User profile |
⚠️ Naming Rules:
- Start with letter, $, or _
- No spaces (use camelCase)
- Case sensitive: age ≠ Age
Example
let name = "Rohan";
let age = 25;
const PI = 3.14;
console.log(name);