What Are Variables?

Variables are containers for storing data values. They allow you to label and reference data in your program. In JavaScript, variables can be declared using var, let, or const.

Example:

let name = "Alice";

Declaring Variables

• var: The old way of declaring variables (function-scoped).
• let: Block-scoped variable declaration (preferred for values that change).
• const: Block-scoped constant declaration (preferred for values that do not change).

Example:

let age = 25;
const pi = 3.14159;

Data Types in JavaScript

JavaScript has several data types, divided into primitive types and objects.

Primitive Types

• String: Text enclosed in quotes. Example: "Hello"
• Number: Numeric values. Example: 42, 3.14
• Boolean: Logical values true or false
• Undefined: A variable declared but not assigned a value
• Null: Represents an intentional "empty" value
• Symbol: A unique and immutable value (introduced in ES6)
• BigInt: Large integers beyond Number’s safe range

Objects

Objects store collections of key-value pairs, arrays, and functions.

Example:

let user = { name: "Alice", age: 25 };

Changing Variable Values

Variables declared with let or var can be reassigned:
let score = 10;
score = 15;

Variables declared with const cannot be reassigned.

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