number nan - nberlette/is GitHub Wiki

@nick/is/number/nan

isNaN

Signature

function isNaN<N = number>(it: N): it is NaN<N>;

Checks if a given value is NaN (not a number). This is a type-safe alias of the global isNaN function,

Parameters
Name Info
it The value to check.
Returns

true if the value is NaN, false otherwise.

Category

Numbers

Tags

number NaN

Examples

import { isNaN } from "jsr:@type/number";

console.log(isNaN(0)); // false
console.log(isNaN(1)); // false
console.log(isNaN(1.5)); // false
console.log(isNaN(NaN)); // true
console.log(isNaN(Infinity)); // false

isNaN

Signature

function isNaN(it: unknown): it is NaN;

Checks if a given value is NaN (not a number). This is a type-safe alias of the global isNaN function,

Parameters
Name Info
it The value to check.
Returns

true if the value is NaN, false otherwise.

Category

Numbers

Tags

number NaN

Examples

import { isNaN } from "jsr:@type/number";

console.log(isNaN(0)); // false
console.log(isNaN(1)); // false
console.log(isNaN(1.5)); // false
console.log(isNaN(NaN)); // true
console.log(isNaN(Infinity)); // false

MaybeNaN

Signature

export type MaybeNaN<N = number> = Cast<N, MAYBE_NAN>;

Casts a value into a partial NaN type. This is a more forgiving form of the NaN type, which allows for the assignment of other numeric values, but still retains the ability to distinguish itself from generic numbers. This is often called a "Flavored" type, whereas the stricter NaN is known as a "Branded" type.

Type Parameters
  • N (default: number)
Category

Numbers

Tags

number NaN

Examples

import { isNaN, type MaybeNaN } from "jsr:@type/number";

let x = NaN as MaybeNaN, y = 0;

if (isNaN(x)) {
  console.log(x);
} else {
  console.log(y);
}

y = NaN; // <- No error! (this is the main difference from `NaN`)

NaN

Signature

export type NaN<N = number> = Cast<N, NAN>;

Casts a value into a branded type that represents the special numeric value NaN (not a number). This is a very strict type, and it prevents any other type from being assigned unless they pass the isNaN type guard. If the value is not a subtype of number, this will resolve to never.

Type Parameters
  • N (default: number)
Category

Numbers

Tags

number NaN

Examples

import { isNan, type NaN } from "jsr:@type/number";

let x = NaN as NaN, y = 0;

if (isNan(x)) {
  console.log(x);
} else {
  console.log(y);
}

// This will raise a TypeScript compiler error:
x = 0; // <- TS2322 Type '0' is not assignable to type 'NaN'.
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