Last Updated: 3/6/2026

P.not Patterns

P.not lets you match on everything but a specific value. It’s a function taking a pattern and returning the opposite pattern.


import { match, P } from 'ts-pattern';
 
type Input = boolean | number;
 
const toNumber = (input: Input) =>
  match(input)
    .with(P.not(P.boolean), (n) => n) // n: number
    .with(true, () => 1)
    .with(false, () => 0)
    .exhaustive();
 
console.log(toNumber(2));
// => 2
console.log(toNumber(true));
// => 1