Just-Maybe

It's a Maybe monad for JavaScript.

Installation

``
> npm install --save-dev just-maybe
`

Usage

`
import { Maybe } from 'just-maybe';


// Create a Maybe from a possible null value.
const maybe: Maybe =
Maybe.fromNullable(getUser());


// Create a Just type
const maybe: Maybe =
Maybe.just(5);


// Create a Nothing type
const maybe: Maybe =
Maybe.nothing();


// Map a maybe, transform a Just value
const mappedMaybe: Maybe =
maybe.map(val: number => val + 5);


// Filter a maybe, return a Nothing if predicate fails
const filteredMaybe: Maybe =
maybe.filter((val: number): boolean => val > 5);


// Chain maybes, use value of a maybe to create a new Maybe
const chainedMaybe: Maybe =
maybe.chain((val: number): Maybe => {
if (val > 5) {
return Maybe.just('is greater than 5');
} else {
return Maybe.nothing();
}
});


// Join maybes, flatten nested Maybes
const nested: Maybe> =
Maybe.just(Maybe.just(5));

const flattened: Maybe =
nested.join();


// Fork a maybe, return value of first function for Just, value of second for Nothing
const value: number =
maybe.fork(
(val: number): number => val * 10,
(): number => 100
);


// Get the value of a Just, throws if a Nothing
const value: number =
maybe.get();


// Get with default, return default if Nothing
const value: number =
maybe.getOrElse(0);
``