ts-result

This library brings elements of functional programming to TypeScript/JavaScript. See Use cases section for details.

Install

npm

npm install @vladbasin/ts-result

yarn

yarn add @vladbasin/ts-result

Use cases

Asynchronous code chaining

Let's assume you have to work with the set of async methods, which load data from backend and return Promise. Normally you use try\catch, async\await, then\catch, if\then\else to handle results. Readability isn't really good with this approach.

showLoader();
try {
    const wallet = await getWalletAsync();
    if (wallet.money < 10) {
        alert("Not enough money");
        return;
    }
    const item = await getItemAsync();
    const response = await purchaseAsync(item);
    if (!response.success) {
        alert(response.error);
        return;
    }
    log("Purchase success");
}
catch (error) {
    alert(error);
}
finally {
    hideLoader();
}

However, with this library instead you can write nice readable chains of methods:

import { Result } from "@vladbasin/Result";

showLoader();
Result
    .FromPromise(getWalletAsync())
    .ensure(wallet => wallet.money > 10, "Not enough money")
    .onSuccess(() => getItemAsync(itemId))
    .onSuccess(item => purchaseAsync(item))
    .ensure(response => response.success, response.error)
    .onFailure(error => alert(error))
    .onSuccess(() => log("Purchase success"))
    .onBoth(result => hideLoader())
    .run();

Rid of primitive obsession

Without this library (poor readability, code repeats)

const usernameValidation = validateUsername(username);
if (!usernameValidation.success) {
    alert(usernameValidation.error)
    return;
}
const passwordValidation = validatePassword(password);
if (!passwordValidation.success) {
    alert(passwordValidation.error)
    return;
}
const passwordRepeatValidation = validatePasswordRepeat(passwordRepeat, password);
if (!passwordRepeatValidation.success) {
    alert(passwordRepeatValidation.error)
    return;
}

With this library (readable code, reusable logic)

import { Result } from "@vladbasin/Result";

Result
    .Start()
    .onSuccess(() => validateUsername(username))
    .onSuccess(() => validatePassword(password))
    .onSuccess(() => validatePasswordRepeat(passwordRepeat, password))
    .onFailure(error => alert(error))
    .run();

Other handy API

This library also provides API to retry(), delay(), and combine() asynchonous code. See inline comments for more documentation