vpagani/lemons.js

🍋 Common algebraïc data types for JS

🍋 Common algebraïc data types for JavaScript, 'cause when life hands you lemons...

Result

Pseudo-type:

type Result<E, T> =
    | Ok T
    | Err E

Usage example:

import Result, { Ok, Err } from 'lemons/Result';
// or: import { Result, Ok, Err } from 'lemons';

const r1: Result<string, number> = Ok(42);
r1.isOk()           // => true
r1.isErr()          // => false
r1.withDefault(99)  // => 42
r1.unwrap()         // => 42

const r2: Result<string, number> = Err('Oops');
r2.isOk()           // => false
r2.isErr()          // => true
r2.withDefault(99)  // => 99
r2.unwrap()         // throws 'Oops'

LazyResult

Pseudo-type:

type LazyResult<E, T> =
    | Initial
    | Loading
    | Failure E
    | Success T

Useful for state management that typically has an initial, loading, and a failure/success outcome state, like page loading, or submitting a form. The following example shows how you would use the LazyResult as part of a React app, but since ADTs are simple data structures, they work with any technology.

Annotated usage example: