What are the different data types in JavaScript?

Question

What are the different data types in JavaScript?

Answer

JavaScript has two broad categories of data types: primitive and non-primitive (or reference) types.

Primitive types:

• string
• number
• boolean
• undefined
• null
• symbol
• bigint

Non-primitive types:

• object (includes arrays, functions, and dates)

Primitive values are immutable and compared by value, while non-primitives are compared by reference.

let x = 5;
let y = 5;
console.log(x === y); // true (same value)

let a = { num: 5 };
let b = { num: 5 };
console.log(a === b); // false (different references)

Real-World Example

When comparing API responses, remember that objects are compared by reference. Even two objects with identical keys and values are considered different unless they point to the same memory reference.

Quick Practice

Log the type of each of the following values using typeof: 42, 'Hello', true, null, undefined, {}, and [].

Summary

JavaScript has 7 primitive types and 1 non-primitive type (object) — knowing how they behave is key to avoiding equality and mutation pitfalls.