J

JavaScript Handbook

Clean • Professional

Primitive Data Types

2 minute

Primitive Data Types in JavaScript

Primitive data types are simple, immutable (unchangeable) values stored directly in memory.

When you copy them into another variable, the value itself is copied, not a reference.

JavaScript has 7 primitive data types:

learn code with durgesh images

Number – The Numeric Type

Represents any number — whole, decimal, or even special values like Infinity and NaN (Not a Number).

  • Math operations, counters, or prices.
const price = 9.99;
let count = 5;

console.log(price + count); // 14.99
console.log(10 / 0);        // Infinity
console.log("abc" * 2);     // NaN

String – Text and Characters

A sequence of characters inside quotes (', ", or ```).

  • Storing names, labels, or messages.
const name = "Ravi";
let greeting = `Hello, ${name}!`;

console.log(greeting);    // Hello, Ravi!
console.log(name + " ji"); // Ravi ji

Boolean – True or False

Represents logical values: true or false.

  • Conditions, toggles, and decision-making.
const isActive = true;
let hasAccess = false;

console.log(isActive && !hasAccess); // true

Undefined – Not Yet Assigned

A variable that has been declared but not assigned any value.

  • To show that something hasn’t been initialized.
let x;
console.log(x); // undefined
console.log(x === undefined); // true

Null – Empty on Purpose

Represents intentional absence of value.

  • Clearing or resetting a variable.
const data = null;
console.log(data === null); // true
console.log(data ?? "Empty"); // Empty

Symbol (ES6) – Unique Identifier

A unique and immutable value, often used as object keys to avoid naming conflicts.

  • Adding private or hidden properties in objects.
const key = Symbol("id");
const obj = { [key]: 123 };

console.log(obj[key]); // 123

BigInt (ES2020) – For Huge Numbers

Represents integers larger than the safe limit for regular numbers (2^53 - 1).

  • Handling very large IDs, timestamps, or cryptographic data.
const big = 12345678901234567890n; // Notice the 'n'
console.log(big + 10n); // 12345678901234567900n

 

Article 0 of 0