Maybe Modad Example

example.js

'use strict';

import Maybe from 'maybe';
import R from 'ramda';

var person = {
	'name' : 'Homer Simpson',
	'address' : {
		'street' : '123 Fake St.',
		'city' : 'Springfield'
	},
	age : 20
};

const state = x => x.state;
const address = x => x.address;
const toUpper = ''.toUpperCase;
const toLower = ''.toLowerCase;
const concat = [].concat;
const age = x => x.age;

const personsState = Maybe.of( person )
	.map( address )
	.map( state )
	.map( toUpper )
	.map( toLower );

console.log( personsState );

const newAge = Maybe.of( person )
	.map( age )
	.map( R.add( 5 ) )
	.map( R.multiply( 10 ) );

console.log( newAge );

const anotherWay = R.map( R.compose( R.add( 5 ), age ) );

console.log( anotherWay( Maybe.of( person ) ) );

maybe.js

// from https://github.com/MostlyAdequate/mostly-adequate-guide/blob/master/ch8.md
'use strict';

const Maybe = function( x ) {
	this.__value = x;
};

Maybe.of = function( x ) {
	return new Maybe( x );
};

Maybe.prototype.isNothing = function() {
	return ( this.__value === null || this.__value === undefined );
};

Maybe.prototype.map = function( f ) {
	return this.isNothing() ? Maybe.of( null ) : Maybe.of( f( this.__value ) );
};

export default Maybe;