import { match } from 'matchexpr'

type Data = { type: 'text', content: string } | { type: 'img', src: string }

type Result = { type: 'ok', data: Data } | { type: 'error', error: Error }

declare const result: Result

const html = match(result, 'type', {
  error: () => <p>Oops! An error occurred</p>,
  ok: ({ data }) =>
    match(data, 'type', {
      text: ({ content }) => <p>{content}</p>,
      img: ({ src }) => <img src={src} />,
    }),
})

features

• very small bundle size (less than 200 bytes)
• concise syntax, no method chaining

usage

pnpm add matchexpr

import { match } from 'matchexpr'

declare const color: 'red' | 'green' | 'blue'

match(color, {
  red: () => 1,
  green: () => 2,
  blue: () => 3,
})

match(color, {
  red: () => 1,
  green: () => 2,
  // ERROR: Property 'blue' is missing
})

match(color, {
  red: () => 1,
  green: () => 2,
  blue: () => 3,
  yellow: () => 4,
  // ERROR: Property 'yellow' is not a valid case
})

inspired by

• gvergnaud/ts-pattern
• rust match
• suchipi/match-discriminated-union