JavaScript Data Types Overview

Data type in JavaScript defines the kind of value a variable can hold. It tells the computer how to interpret and use that value, such as numbers, text, true/false, or more complex structures like objects and arrays. In JavaScript, data types are mainly divided into two categories:

1. Primitive Data Types
2. Non-Primitive Data Types

Primitive Data Types

Primitive types are immutable, meaning their values cannot be changed once created. They are stored by value.

• String
• Number
• BigInt
• Boolean
• Undefined
• Null
• Symbol

Non-Primitive Data Types (Objects)

Reference types are mutable and stored by reference. They include objects, arrays, and functions.

• Object
• Array
• Function

Summary Table

Type	What It Is	Example	Use Case
Number	Numbers (int, decimal)	const x = 42.5;	Math, counts
String	Text	let s = "Hi";	Names, messages
Boolean	true or false	const b = true;	Conditions
Undefined	No value set	let u;	Missing data
Null	Intentional no value	const n = null;	Reset data
Symbol	Unique ID	const s = Symbol("id");	Unique keys
BigInt	Huge integers	const b = 123n;	Large numbers
Object	Key-value pairs, arrays	const o = { key: 1 };	Complex data