Package Exports

go-result-js

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (go-result-js) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

go-result-js

Go-like results:

const [ err, result ] = foo();

Zero dependencies
Full typescript support
100% test coverage

Usage

Install:

npm i go-result-js

Import:

import { ResultA, ResultErr, ResultOk } from 'go-result-js';

Or use it globally:
(write in main file, before everythink)

import 'go-result-js/lib/global';

Example with exceptions

Before:

const result = await doSmthWithException();
// (node:17320) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): Error: Request failed with status code 400
// (node:17320) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

After:

const [ err, result ] = await ResultA(doSmthWithException());
if (err || !result) {
    // exception handled!
}

Example

function divide(a: number, b: number): Result<number> {
    if (b === 0) return ResultErr('Can not divide by zero!');
    return ResultOk(a / b);
}

function main() {
    const [ err, result ] = divide(10, 5);

    if (err) console.error(err);
    else console.log('success', result);
}

Example with async

const asyncDivide = (a: number, b: number): ResultA<number> => ResultA<number>(resolve => {
    resolve(b === 0 ? new Error('Can not divide by zero!') : a / b);
});

async function asyncMain() {
    const [ err, result ] = await asyncDivide(10, 5);

    if (err) console.error(err);
    else console.log('success', result);
}

Example with AWS

import { Auth } from 'aws-amplify';

export async function main() {
    const [ err, user ] = await ResultA(Auth.signIn('root', 'password'));
}

Multiple results

Handle multiple ResultA results, and catch any errors.

const { err, values } = await resultAll(
    Content.fetchById(contentType, id),
    Rubrics.fetchRubrics(),
    ContentTypes.fetchContentTypes(),
);

if (err) {
    // on any error
}

const {
    0: content,
    1: rubrics,
    2: contentTypes,
} = values;

API

Types

export type ResultErr<ErrorT extends Error = Error> = ErrorT|true|undefined;
export type Result<T, ErrorT extends Error = Error> = [ ResultErr<ErrorT>, T|undefined ];
export type ResultA<T, ErrorT extends Error = Error> = Promise<Result<T, ErrorT>>;

Methods

function registerGlobally(global?: any): Result<boolean>

Assign all methods to global object.
go-result-js/lib/global calls it.

function ResultOk<T>(value: T): Result<T>

Returns value with undefined error.

function ResultErr<ErrorT extends Error, T=any>(err: ErrorT|true|string = true): Result<T, ErrorT>

Returns error with undefined value.

function ResultA<T, ErrorT extends Error>(
    x: Promise<T> | ((
        resolve: (value: undefined|T|Error) => void,
        reject: (err?: ErrorT) => void
    ) => void)
): ResultA<T, ErrorT>

Takes Promise's callbacks or Promise, catch it's error and resolve as Promise<Result>.

function resultAll<Results extends ResultA<any>[]>(
    ...results: Results
): Promise<{
    err: ResultErr | undefined,
    values: {
        [i in keyof Results]: PickSecondItem<PromiseType<Results[i]>, undefined>
    },
    results: {
        [i in keyof Results]: PromiseType<Results[i]>
    }
}>