🎯 Learning Objectives

By the end of this class, students will be able to:

• Understand what data types are and why they matter.
• Distinguish between primitive and non-primitive data types.
• Understand by value vs by reference behavior.
• Know what mutable and immutable mean.
• Use the typeof operator correctly.
• Type Conversion
• Explain and use the Symbol data type.

🧩 1. What Are Data Types?

Every variable in JavaScript holds a value — that value has a type.

For example:

let name = "Hammad";   // String
let age = 22;          // Number
let isStudent = true;  // Boolean

👉 Data types define what kind of data a variable can store and how it behaves when used.

🧭 2. Checking Data Types Using typeof

We can check the data type of any variable using the typeof operator.

📘 Example:

	let name = "Ali";
	let age = 21;
	let isOnline = false;

console.log(typeof name);     // "string"
console.log(typeof age);      // "number"
console.log(typeof isOnline); // "boolean"

⚠️ Special Case:

console.log(typeof null); // "object" (This is a known JavaScript bug!)