hydrogen

hydrogen

A minimal library for object-oriented JavaScript development.

How To Use

Node.js

Add hydrogen to your dependencies, then run:

npm install

Then add:

var h = require('hydrogen');

Browser

<script type="text/javascript" src="path/to/hydrogen.js"></script>

Usage Examples

See examples for the ones below plus more.

Inheritance

h.create() can be used to create a prototypical object, or extend one prototypical object from another.

function Character(name, mediumName, otherName) {
    this.name = name;
    this.mediumName = mediumName;
    this.otherName = otherName;
}
h.create(Character, {
    getDescription: function() {
        return this.getName() + ' is from "' + this.mediumName + '"';
    },
    getName: function() {
        if (this.otherName) {
            return this.name + ' (a.k.a. ' + this.otherName + ')';
        } else {
            return this.name;
        }
    }
});

function Villain(name, mediumName, otherName, wearsMask) {
    this.super.constructor.call(this, name, mediumName, otherName);
    this.wearsMask = wearsMask;
}
h.create(Villain, Character, {
    getDescription: function() {
        return this.getName() + ' is from "' + this.mediumName + '". Mwahahaha!';
    }
});

var mcclane = Character.makeInst('John McClane', 'Die Hard');
mcclane.name; // John McClane
mcclane.getDescription(); // John McClane is from "Die Hard"
var vader = Villain.makeInst('Darth Vader', 'Star Wars', 'Anakin Skywalker', true);
vader.getDescription(); // Darth Vader (a.k.a. Anakin Skywalker) is from "Star Wars". Mwahahaha!

Private Variables

h.attach() adds a closure to an object, which can be used to contain private variables and functions.

function Weapon(name) {
    this.name = name;
}
h.attach(Weapon, function() {
    var users = [];

    return {
        addUser: function(user) {
            users.push(user);
        },
        getUsers: function() {
            return users;
        }
    };
});

var bullwhip = Weapon.makeInst('Bullwhip');
bullwhip.users; // undefined
bullwhip.addUser('Indiana Jones');
bullwhip.addUser('Catwoman');
bullwhip.getUsers(); // Indiana Jones,Catwoman

Properties returned by an attached closure can be overridden in a child object via either h.create() or h.attach(), see examples.

Checking Interfaces

h.checkImpl() checks a value against an "interface" and determines if the value is a valid implementation of the interface.

var IMovie = {
    type: 'object',
    contents: {
        title: {
            type: 'string'
        },
        details: {
            type: 'object',
            contents: {
                summary: {type: 'string'},
                year: {type: 'number'}
            }
        },
        play: {
            type: 'function',
            minArity: 2
        }
    }
};

var minorityReport = {
    title: 'Minority Report',
    details: {
        summary: 'In a future where a special police unit is able to arrest murderers before ' +
            'they commit their crimes, an officer from that unit is himself accused of a future murder.',
        year: 2002,
        cast: [
            'Tom Cruise',
            'Colin Farrell',
            'Samantha Morton',
            'Max von Sydow'
        ]
    },
    play: function(startTime, fullScreen, showSubtitles) {}
};

var warOfTheWorlds = {
    title: 'War of the Worlds',
    details: {
        summary: 'As Earth is invaded by alien tripod fighting machines, one family fights for survival.',
        year: 2005
    },
    play: function(fullScreen) {}
};

h.checkImpl(minorityReport, IMovie); // true
h.checkImpl(warOfTheWorlds, IMovie); // At key ["play"]: Function does not accept at least 2 parameters

See examples for more.