TypeScript Result

Supercharge your TypeScript error handling with a powerful Result type that transforms chaotic try-catch blocks into elegant, type-safe code—catching bugs at compile time while making async operations seamless and your code much harder to break.

Features

• 🐞 Catch bugs at compile time

  TypeScript's type system tracks every possible failure scenario and forces you to handle them

• 🧩 Simple and tiny, yet very powerful

  Thanks to the polymorphic operators, you only need to learn a few methods. And notice the small footprint: Only 1.9 KB minified and gzipped.

• ✨ Full type inference without boilerplate

  Just return Result.ok() or Result.error() and let TypeScript do the heavy lifting

• ⚡ Seamless async support

  Work with async operations without constant await calls through automatic AsyncResult conversion

• 🔗 Chaining and generator styles

• 📦 Zero dependencies

Links

• Docs
• Examples
• Playground

Example

Reading a JSON config file and validating its contents:

import fs from "node:fs/promises";
import { Result } from "typescript-result";
import { s } from "some-schema-validation-library";

class IOError extends Error {
  readonly type = "io-error";
}

class ParseError extends Error {
  readonly type = "parse-error";
}

class ValidationError extends Error {
  readonly type = "validation-error";
}

const readFile = Result.wrap(
  (filePath: string) => fs.readFile(filePath, "utf-8"),
  (error) => new IOError(`Unable to read file`, { cause: error }),
);

const parseConfig = Result.wrap(
  (data: unknown) =>
    s
      .object({
        name: s.string().min(1),
        version: s.number().int().positive(),
      })
      .parse(data),
  (error) => new ValidationError(`Invalid configuration`, { cause: error }),
);

// chaining style:
const result = await readFile("config.json")
  .mapCatching(
    (contents) => JSON.parse(contents),
    (error) => new ParseError("Unable to parse JSON", { cause: error }),
  )
  .map((json) => parseConfig(json));

// generator style:
const result = await Result.gen(function* () {
  const contents = yield* readFile("config.json");

  const json = yield* Result.try(
    () => JSON.parse(contents),
    (error) => new ParseError("Unable to parse JSON", { cause: error }),
  );

  return parseConfig(json);
});

const [config, error] = result.toTuple();

if (error) {
  switch (error.type) {
    case "io-error":
      return "Please check if the config file exists and is readable";
    case "parse-error":
      return "Please check if the config file contains valid JSON";
    case "validation-error":
      return error.message;
  }
}

return `Successfully read config: name => ${config.name}, version => ${config.version}`;

For more examples, please check out the other examples.

Installation

Install using your favorite package manager:

npm install typescript-result

Requirements

Typescript

Technically Typescript with version 4.8.0 or higher should work, but we recommend using version >= 5 when possible.

Also it is important that you have strict or strictNullChecks enabled in your tsconfig.json:

{
  "compilerOptions": {
    "strict": true
  }
}

Runtimes

Tested with Node.js version 16 and higher, but this library should work with all modern browsers/runtimes.