StacklessError and Result for typescript

Example.ts

function tryParse(str: string): Result<unknown> {
  try {
    return Result.ok(JSON.parse(str));
  } catch (e) {
    return Result.err((e as Error).message);
  }
}

const parseResult = tryParse('{ "hello": "world" }');
if (parseResult.isErr) {
  console.error(parseResult.error);
  return;
}

const obj = parseResult.value;
console.log(obj);

Result.ts

import { StacklessError } from 'StacklessError';

export type Ok<T> = {
  readonly isOk: true;
  readonly isErr: false;
  readonly value: T;
};

export type Err<E extends Error = Error> = {
  readonly isOk: false;
  readonly isErr: true;
  readonly error: E;
};

export type Result<T = undefined, E extends Error = Error> = Ok<T> | Err<E>;

function ok<T = undefined>(value?: T): Result<T, never> {
  return {
    isOk: true,
    isErr: false,
    value: value as T,
  } as const;
}

function err<E extends Error = Error>(error: E): Result<never, E>;
function err<E extends Error = Error>(error: string, data?: unknown): Result<never, E>;
function err<E extends Error = Error>(error: E | string, data?: unknown): Result<never, E> {
  return {
    isOk: false,
    isErr: true,
    error: typeof error === 'string' ? (new StacklessError(error, data) as E) : error,
  } as const;
}

function resultTry<T, E extends Error = Error>(fn: () => T): Result<T, E> {
  try {
    return ok(fn());
  } catch (e) {
    return err<E>(e);
  }
}

export const Result = {
  ok,
  err,
  try: resultTry,
};

StacklessError.ts

import { inherits } from 'util';

export class StacklessError {
  readonly data?: unknown;
  readonly message: string;
  readonly name: string;

  constructor(message = '', data?: unknown) {
    this.name = this.constructor.name;
    this.message = message;
    this.data = data;
  }
}

// new StacklessError('') instanceof Error === true
inherits(StacklessError, Error);

// Object.prototype.toString.call(new StacklessError) === '[object Error]'
Object.defineProperty(StacklessError.prototype, Symbol.toStringTag, {
  value: 'Error', writable: false, configurable: false, enumerable: false,
});