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Tuples Arrays

Last Updated: 3/6/2026

Tuple and Array Patterns

Tuples (arrays)

In TypeScript, Tuples  are arrays with a fixed number of elements that can be of different types. You can pattern-match on tuples using a tuple pattern. A tuple pattern will match if the input value is an array of the same length, and each item matches the corresponding sub-pattern.

import { match, P } from 'ts-pattern';
 
type Input =
  | [number, '+', number]
  | [number, '-', number]
  | [number, '*', number]
  | ['-', number];
 
const input = [3, '*', 4] as Input;
 
const output = match(input)
  .with([P._, '+', P._], ([x, , y]) => x + y)
  .with([P._, '-', P._], ([x, , y]) => x - y)
  .with([P._, '*', P._], ([x, , y]) => x * y)
  .with(['-', P._], ([, x]) => -x)
  .exhaustive();
 
console.log(output);
// => 12

P.array patterns

To match on arrays of unknown size, you can use P.array(subpattern). It takes a sub-pattern, and will match if all elements in the input array match this sub-pattern.

import { match, P } from 'ts-pattern';
 
type Input = { title: string; content: string }[];
 
let input: Input = [
  { title: 'Hello world!', content: 'This is a very interesting content' },
  { title: 'Bonjour!', content: 'This is a very interesting content too' },
];
 
const output = match(input)
  .with(
    P.array({ title: P.string, content: P.string }),
    (posts) => 'a list of posts!'
  )
  .otherwise(() => 'something else');
 
console.log(output);
// => 'a list of posts!'

Matching variadic tuples with P.array

In TypeScript, Variadic Tuple Types  are array types created with the ... spread operator, like [string, ...string[]], [number, ...boolean[], string] etc. You can match against variadic tuple types using array literals containing ...P.array(subpattern):

import { match, P } from 'ts-pattern';
 
type Input = (number | string)[];
 
declare const input: Input;
 
const output = match(input)
  // P.array's parameter is optional
  .with([P.string, ...P.array()], (input) => input) // input: [string, ...(number | string)[]]
  .with(['print', ...P.array(P.string)], (input) => input) // input: ['print', ...string[]]
  // you can put patterns on either side of `...P.array()`:
  .with([...P.array(P.string), 'end'], (input) => input) // input: [...string[], 'end']
  .with(['start', ...P.array(P.string), 'end'], (input) => input) // input: ['start', ...string[], 'end']
  .otherwise((input) => input);
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