isundefined - datatype/isundefined.ts

function isundefined



isundefined(x: unknown): x is undefined

Checks if the input is undefined.

Returns true if the input is strictly equal to undefined, otherwise returns false.

Examples

import { assertEquals } from "jsr:@std/assert";

assertEquals(isundefined(undefined), true);

import { assertEquals } from "jsr:@std/assert";

assertEquals(isundefined(null), false);

import { assertEquals } from "jsr:@std/assert";

assertEquals(isundefined('test'), false);



x: unknown

The element to check.

x is undefined

Returns true if x is undefined, otherwise false.