JS Data Types

JavaScript is dynamically typed — a variable can hold any type of data, and the type can change at runtime. Use typeof to check any variable’s type.

Try It — All Data Types

Data Types at a Glance

Type	Example	typeof result
String	"Hello"	"string"
Number	42, 3.14	"number"
Boolean	true, false	"boolean"
Undefined	let x;	"undefined"
Null	null	"object" (JS quirk)
Object	{ key: value }	"object"
Array	[1, 2, 3]	"object"

Tip: Arrays are technically objects in JavaScript. Use Array.isArray(value) to reliably test if something is an array.