falsy - nberlette/is GitHub Wiki

@nick/is/falsy

isFalsy

Signature

function isFalsy(it: unknown): it is Falsy;

Check if the given value is falsy.

Parameters
Name Info
it The value to check.
Returns

true if the value is falsy, false otherwise.

Examples

import { isFalsy } from "@nick/is/falsy";

isFalsy(null); // true
isFalsy(undefined); // true
isFalsy(0); // true
isFalsy(""); // true
isFalsy(false); // true
isFalsy([]); // false

Falsy

Signature

export type Falsy = null | undefined | void | false | 0 | 0n | "" | NaN;

A type that represents all falsy values.

Category

Primitives

IsFalsy

Signature

export type IsFalsy<T, True = true, False = false> = [T] extends [never] ? False
  : [Exclude<T, Falsy>] extends [never] ? True
  : False;

If type T is falsy, returns True (default: true), otherwise returns False (default: false).

Type Parameters
  • T
  • True (default: true)
  • False (default: false)
Category

Types

Examples

Signature

type X = IsFalsy<null>; // true
type Y = IsFalsy<"">; // true
type Z = IsFalsy<0>; // true
type A = IsFalsy<false>; // true
type B = IsFalsy<[]>; // false
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