generic-result-type

A small, dependency free Result type for TypeScript and JavaScript.

It provides a simple way to represent success or failure values without throwing exceptions.

Installation

npm i generic-result-type

Module support

This package supports both ESM and CommonJS out of the box.

ESM:

import { success, failure, type Result } from 'generic-result-type';

CommonJS:

const { success, failure } = require('generic-result-type');

TypeScript typings are included.

No dependencies

This package has zero runtime dependencies. It does not rely on any external libraries.

Usage

Create results using the success and failure functions, then narrow them with the provided type guards.

Example function

const parseNumber = (input: string): Result<number> => {
  const value = Number(input);

  if (Number.isNaN(value)) {
    return failure(Error('Not a number'));
  }

  return success(value);
}

Handling results

Use the type guard helpers to safely branch on the result type.

const result = getSomeValue();

if (isErrorResult(result)) { // or if (result.success === false)
  console.error('Error:', result.error.message);
  return;
}

console.log('Value:', result.value);

TypeScript will correctly narrow the type inside each branch without casting.

Mapping

You can map the value or the error of a Result with these methods:

• map
• mapErr
• mapAsync
• mapErrAsync

const numberResult = getSomeNumberResult().map(x => x * 2);

const responseResult = await getSomeStringResult().mapAsync(async x => fetch(x));

License

ISC