Type Alias LessThan<A, B>

LessThan: GreaterThanOrEqual<A, B> extends infer Result
? Result extends true ? false : true
: never

Returns a boolean for whether a given number is less than another number.

Type Parameters

A extends number
B extends number

Example

import type {LessThan} from 'type-fest';

type A = LessThan<1, -5>;
//=> false

type B = LessThan<1, 1>;
//=> false

type C = LessThan<1, 5>;
//=> true

Note: If either argument is the non-literal number type, the result is boolean.

Example

import type {LessThan} from 'type-fest';

type A = LessThan<number, 1>;
//=> boolean

type B = LessThan<1, number>;
//=> boolean

type C = LessThan<number, number>;
//=> boolean

Example

import type {LessThan} from 'type-fest';

// Use `LessThan` to constrain a function parameter to negative numbers.
declare function setNegative<N extends number>(value: LessThan<N, 0> extends true ? N : never): void;

setNegative(-1); // ✅ Allowed
setNegative(-2); // ✅ Allowed

// @ts-expect-error
setNegative(0);

// @ts-expect-error
setNegative(1);