nanocase

Small, exhaustive matching for TypeScript discriminated unions.

import { match } from "nanocase";

type Shape =
  | { kind: "circle"; radius: number }
  | { kind: "square"; size: number };

const area = (shape: Shape) =>
  match(shape).on("kind", {
    circle: ({ radius }) => Math.PI * radius ** 2,
    square: ({ size }) => size ** 2,
  });

Missing cases are TypeScript errors.

Patterns

import { match } from "nanocase/pattern";

match(shape, (m) =>
  m.with({ kind: "circle" }, () => "round").otherwise(() => "other"),
);