typeof

Examples

The types of basic values:

console.log(typeof 42);
console.log(typeof 'hi');
console.log(typeof true);
console.log(typeof undefined);
console.log(typeof (() => {}));

Output:

number
string
boolean
undefined
function

Surprising results:

console.log(typeof null);
console.log(typeof []);
console.log(typeof NaN);

Output:

object
object
number

Notes

typeof null returns object — an old language bug that can never be fixed. Arrays also give object, so check arrays with Array.isArray() and null with value === null.

The possible answers are undefined, boolean, number, bigint, string, symbol, function and object.