isNotUndefined function

Checks whether a value is not undefined; null passes, unlike with isDefined.

import { isNotUndefined } from 'utils';

Signature

export function isNotUndefined<T>(value: T): value is Exclude<T, undefined>

Parameters

Name	Description
T	The type of the value.
value	The value to check.

Returns

true for anything but undefined.

Example

[1, null, undefined].filter(isNotUndefined); // [1, null], typed (number | null)[]

Tests

Line coverage: 100 %.

• ✅ excludes undefined only

Source

src/guard/is-not-undefined.ts (on GitHub)

Source code

/**
 * Checks whether a value is not `undefined`; `null` passes, unlike with `isDefined`.
 *
 * @template T - The type of the value.
 * @param value - The value to check.
 * @returns `true` for anything but `undefined`.
 * @example
 * [1, null, undefined].filter(isNotUndefined); // [1, null], typed (number | null)[]
 */
export function isNotUndefined<T>(value: T): value is Exclude<T, undefined> {
  return value !== undefined;
}

Test file

import { isNotUndefined } from './is-not-undefined';

describe(isNotUndefined, () => {
  it('excludes undefined only', () => {
    expect([0, null, undefined].filter(isNotUndefined)).toStrictEqual([0, null]);
  });
});

Keywords: is, not, undefined, guards, function