giftbox

A lightweight Javascript library for the Option monad. Maybe there's something in it, maybe there isn't ;)

$ npm install giftbox

var Option = require('giftbox').Option;

Option('hello world');					// Some
Option(undefined);						// None
Option('hello world').get();			// 'hello world'
Option(null).getOrElse('pied piper');	// 'pier piper'

Giftbox aims to provide a wrapper API around absent values and is highly motivated by Scala's Option.

One of big source of bugs in production environments is missing data represented by nulls, undefined, empty strings, etc. Traditionally calling methods on null or 'empty' values causes NPE's, etc. and forces developers to create disorganized utilities with null/empty checks all over the codebase, adding further complexity.

Overview

Giftbox provides 3 simple classes to handle optional data - Option, Some & None. Here's how to use them:

Simple Examples

Where Giftbox becomes powerful is when you have some logic that returns data and you need to handle that data:

var userDetails = userFetcher('[email protected]');

if(Option(userDetails).isDefined()) {
	render(userDetails);
}

// A more functional form:
Option(userDetails).map(render);

// Wrap a method return value in Option:
var userFetcher = function(email) {
	return Option(userClient.findByEmail(email));
};

userFetcher('[email protected]').map(render).getOrElse(renderNotFound);

Advanced Examples

Building a user subscription UI

// lets fetch a user
userFetcher('[email protected]');

// then lets fetch their subscription record
userFetcher('[email protected]').map(function(user) {
	return subscriptionFetcher(user.id); // returns Option(subscription)
});

// but what if they have no subscription?
userFetcher('[email protected]').map(function(user) {
	// returns either subscription or message
	subscriptionFetcher(user.id).getOrElse('No Subscriptions Found');
});

// ok lets render what we got
userFetcher('[email protected]').map(function(user) {
	renderUI(subscriptionFetcher(user.id).getOrElse('No Subscriptions Found'));
});

// but what if there was no user?
userFetcher('[email protected]').map(function(user) {
	renderUI(subscriptionFetcher(user.id).getOrElse('No Subscriptions Found'));
}).getOrElse(
	redirectToLoginPage();
);

Finding Player Score

var lookupPlayer = function(id) {
	return userFetcher(id); // returns Option(user)
};

var lookupScore = function(player) {
	return scoreFetcher(player); // returns Option(number)
};

var scoreFilter = function(score) {
	return score > 105
};

showScore(lookupPlayer(1).map(lookupScore));
=> Some(Some(103))

// we don't want to render 'Some(103)'
showScore(lookupPlayer(1).flatMap(lookupScore));
=> Some(103)

// great, but we only want to show the score if it is above 105
showScore(lookupPlayer(1).flatMap(lookupScore).filter(scoreFilter));
=> None

// but lets show a default value if player not found or 
// score not found or score not above 105
showScore(
	lookupPlayer(1)
		.flatMap(lookupScore)
		.filter(scoreFilter)
		.getOrElse('Lets start a new game here!')
);
=> 'Lets start a new game here!'

API

Giftbox considers the following "absent" or "empty": null, undefined and NaN.

isDefined

Returns true if the val is not empty.

Option(val).isDefined();

get

Returns val (whether or not it's empty).

Option(val).get();

getOrElse

Returns val if it isDefined otherwise returns elseval.

Option(val).getOrElse(elseVal);

orElse

Returns val if it isDefined otherwise uses alternative as an Option provider.

Option(val).orElse(alternative);

orNull

Returns val if it isDefined otherwise returns null.

Option(val).orNull(alternative);

map

Maps val if it isDefined using the callback function and returns Some(callback(val)) else returns None;

Option(val).map(callback);

flatMap

Flattens nested mapping calls over val if it isDefined using the callback function and returns Some else returns None;

Option(val).flatMap(function(v1) {
	return Option(modify1(v)).flatMap(function(v2) {
		return Option(modify2(v2));
	}
});

filter

Applies predicate to val if it isDefined and returns Some(val) if it passes and None if it fails.

Option(val).filter(predicate);

filterNot

Opposite of filter.

Option(val).filterNot(predicate);

foreach

Applies the callback function to val if it isDefined and doesn't return anything.

Option(val).foreach(callback);

match

Applies someCallback on val if it isDefined otherwise applies noneCallback.

Option(val).match(someCallback, noneCallback);

collect

Applies predicate on val if it isDefined and maps val using callback.

Option(val).collect(predicate, callback);

toArray

Transforms option to an array.

Option(val).toArray();

Contribution

Please contribute to Giftbox via GitHub issues. Would be great if all new code is submitted with tests and documentation. Lets discuss features and bugs there as well!