#Result vs throw

// Example of a post deletion function
type 
type PostDeleteError = PostNotFoundError | PostPermissionError | PostAlreadyDeletedErrorPostDeleteError = (
  | 
class PostNotFoundErrorPostNotFoundError
  | 
class PostPermissionErrorPostPermissionError
  | 
class PostAlreadyDeletedErrorPostAlreadyDeletedError
);

const 
const deletePost: (postId: string) => Result.ResultAsync<void, PostDeleteError>deletePost = async (
postId: stringpostId: string): 
import ResultResult.
type ResultAsync<T, E> = Promise<Result.Result<T, E>>
An asynchronous variant of
Result
, wrapped in a Promise.
@typeParamT  - The type of the Success value.@typeParamE  - The type of the Failure value.@example
import { Result } from '@praha/byethrow';

const fetchData = async (): Result.ResultAsync<string, Error> => {
  try {
    const data = await fetch('...');
    return { type: 'Success', value: await data.text() };
  } catch (err) {
    return { type: 'Failure', error: err as Error };
  }
};
@categoryCore  TypesResultAsync<void, 
type PostDeleteError = PostNotFoundError | PostPermissionError | PostAlreadyDeletedErrorPostDeleteError> => {
  // Business logic errors that should be handled by the application
}

// Example of an infrastructure-level function
const 
const connectToDatabase: () => Promise<Database>connectToDatabase = async (): 
interface Promise<T>
Represents the completion of an asynchronous operationPromise<Database> => {
  // This function may throw errors like connection failures, timeouts, etc.
};

import { 
const ErrorFactory: {
    <Name extends string, Message extends string, Fields extends ErrorFields>(props: {
        name: Name;
        message: Message | ((fields: Fields) => Message);
        fields?: Fields;
    }): ErrorConstructor<Name, Message, Fields>;
    fields<Fields extends ErrorFields>(): Fields;
}
ErrorFactory } from '@praha/error-factory';

class 
class UnexpectedErrorUnexpectedError extends 
ErrorFactory<"UnexpectedError", "An unexpected error occurred", ErrorFields>(props: {
    name: "UnexpectedError";
    message: "An unexpected error occurred" | ((fields: ErrorFields) => "An unexpected error occurred");
    fields?: ErrorFields | undefined;
}): (new (options?: ErrorOptions) => Error & Readonly<{
    name: "UnexpectedError";
    message: "An unexpected error occurred";
}>) & {
    name: "UnexpectedError";
}
ErrorFactory({
  
name: "UnexpectedError"name: 'UnexpectedError',
  
message: "An unexpected error occurred" | ((fields: ErrorFields) => "An unexpected error occurred")message: 'An unexpected error occurred',
}) {}

import { 
import ResultResult } from '@praha/byethrow';

// Wrap potentially throwing operations
const 
const safeDatabaseOperation: (id: string) => Result.ResultAsync<string, UnexpectedError>safeDatabaseOperation = 
import ResultResult.
try<(id: string) => Promise<string>, UnexpectedError>(options: {
    try: (id: string) => Promise<string>;
    catch: (error: unknown) => UnexpectedError;
}): (id: string) => Result.ResultAsync<string, UnexpectedError> (+7 overloads)
export try
Wraps a function execution (sync or async) or a Promise in a
Result
or
ResultAsync
type,
capturing errors and returning them in a structured way.
You can use either a custom catch handler or rely on the safe: true option
to assume the function cannot throw.
@function@typeParamT  - The function type to execute (sync or async) or a Promise type.@typeParamE  - The error type to return if catch is used.@example
Sync  try-catch
import { Result } from '@praha/byethrow';

const fn = Result.try({
try: (x: number) => {
if (x < 0) throw new Error('Negative!');
return x * 2;
},
catch: (error) => new Error('Oops!', { cause: error }),
});

const result = fn(5); // Result.Result<number, Error>
@example
Sync  try-catch with immediate execution
import { Result } from '@praha/byethrow';

const result = Result.try({
immediate: true,
try: () => {
const x = Math.random() * 10 - 5;
if (x < 0) throw new Error('Negative!');
return x * 2;
},
catch: (error) => new Error('Oops!', { cause: error }),
});

// result is Result<number, Error>
@example
Sync  safe
import { Result } from '@praha/byethrow';

const fn = Result.try({
safe: true,
try: (x: number) => x + 1,
});

const result = fn(1); // Result.Result<number, never>
@example
Sync  safe with immediate execution
import { Result } from '@praha/byethrow';

const result = Result.try({
safe: true,
immediate: true,
try: () => Math.random() + 1,
});

// result is Result<number, never>
@example
Async  try-catch
import { Result } from '@praha/byethrow';

const fn = Result.try({
try: async (id: string) => await fetch(`/api/data/${id}`),
catch: (error) => new Error('Oops!', { cause: error }),
});

const result = await fn('abc'); // Result.ResultAsync<Response, Error>
@example
Async  try-catch with immediate execution
import { Result } from '@praha/byethrow';

const result = Result.try({
immediate: true,
try: () => fetch('/api/data'),
catch: (error) => new Error('Fetch failed', { cause: error }),
});

// result is ResultAsync<Response, Error>
@example
Async  safe
import { Result } from '@praha/byethrow';

const fn = Result.try({
safe: true,
try: async () => await Promise.resolve('ok'),
});

const result = await fn(); // Result.ResultAsync<string, never>
@example
Async  safe with immediate execution
import { Result } from '@praha/byethrow';

const result = Result.try({
safe: true,
immediate: true,
try: () => Promise.resolve('ok'),
});

// result is ResultAsync<string, never>
@categoryCreatorstry({
  
try: (id: string) => Promise<string>try: (
id: stringid: string) => {
    // This might throw database query errors, network errors, etc.
    return 
const performDatabaseOperation: (id: string) => Promise<string>performDatabaseOperation(
id: stringid);
  },
  
catch: (error: unknown) => UnexpectedErrorcatch: (
error: unknownerror) => new 
constructor UnexpectedError(options?: ErrorOptions): UnexpectedErrorUnexpectedError({ 
ErrorOptions.cause?: unknowncause: 
error: unknownerror }),
});

// Usage
const 
const result: Result.Result<string, UnexpectedError>result = await 
const safeDatabaseOperation: (id: string) => Result.ResultAsync<string, UnexpectedError>safeDatabaseOperation('123');
if (
import ResultResult.
const isFailure: <UnexpectedError>(result: Result.Result<unknown, UnexpectedError>) => result is Result.Failure<UnexpectedError>
Type guard to check if a
Result
is a
Failure
.
@function@typeParamE  - The type of the error value.@paramresult  - The Result to check.@returnstrue if the result is a Failure, otherwise false.@example
import { Result } from '@praha/byethrow';

const result: Result.Result<number, string> = { type: 'Failure', error: 'Something went wrong' };
if (Result.isFailure(result)) {
  console.error(result.error); // Safe access to error
}
@categoryType  GuardsisFailure(
const result: Result.Result<string, UnexpectedError>result)) {
  // You now have a clean UnexpectedError with your application's stack trace
  // instead of deep library stack traces
  
var console: Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:

A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr

Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@seesourceconsole.
Console.error(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stderr with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const code = 5;
console.error('error #%d', code);
// Prints: error #5, to stderr
console.error('error', code);
// Prints: error 5, to stderr

If formatting elements (e.g. %d) are not found in the first string then
util.inspect() is called on each argument and the
resulting string values are concatenated. See util.format()
for more information.
@sincev0 .1.100error(
const result: Result.Failure<UnexpectedError>result.
error: UnexpectedErrorerror.
Error.stack?: string | undefinedstack);
  // Original error is still accessible
  
var console: Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:

A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr

Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@seesourceconsole.
Console.error(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stderr with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const code = 5;
console.error('error #%d', code);
// Prints: error #5, to stderr
console.error('error', code);
// Prints: error 5, to stderr

If formatting elements (e.g. %d) are not found in the first string then
util.inspect() is called on each argument and the
resulting string values are concatenated. See util.format()
for more information.
@sincev0 .1.100error(
const result: Result.Failure<UnexpectedError>result.
error: UnexpectedErrorerror.
Error.cause?: unknowncause);
}