not

Creates a function that returns the boolean-inverted value of the provided function's result.

Syntax

not<T extends (...args: any[]) => boolean>(callback: T): (...args: Parameters<T>) => boolean

Parameters

Name	Type	Description
callback	T	Function whose result will be inverted.

Returns

Type	Description
(...args: Parameters<T>) => boolean	Function that returns the boolean-inverted value.

Example

const isEven = (x: number) => x % 2 === 0;
const isOdd = not(isEven);
isOdd(3); // true
isOdd(4); // false

Notes

• Throws a TypeError if the argument is not a function.
• Useful for creating inverse predicates in a functional way.

References

• MDN: Logical NOT