HTML5 entity-component game engine
JavaScript Ruby Other
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An HTML5 javascript game engine utlizing the entity-component design. Write highly flexible code in a powerful javascript framework.

EntityJS is currently being rewritten

Version 0.5.0 is moving away from ruby to a nodejs package. The game engine is also moving towards an entity-system design pattern. Checkout the dev branch for the latest updates.

What makes this different from other javascript game engines?

Entity strives to be the most flexible game engine available. We understand no one likes rewritting the same functions and lines of code over and over. So we have developed a solution to this problem and that is the component-entity design. The traditional approach to game engine design is creating a hierarchy of classes. This is infact the most tightly coupled design. This creates close coupled classes whos functionality is strictly typed to one class, its not easily portable to other projects, good luck copying that one needed function and as game development progresses classes get bigger and more complex. You will eventually end up with god-classes who control most of the game logic.

This becomes a big mess.

In the world of entity-component designs. All logic is implemented in a component, as big or small as you want. You can then create an entity and add/remove components to it. The entity is a live represantation of all its components. With this low coupling of components and entities you can mix and match components together to create powerful functionality yet still portable and robust.


You must have at least Ruby 1.8.1+.


EntityJS is now an easy to install gem. In the terminal type in:

gem install entityjs

This will install the latest version of the gem and now you can easily create some games!


When using these commands make sure you are always in the root directory of your game.

Creating a New Game

Creating a game is simple, move to any directory and type in:

entityjs new mygame

This will create a new game using the default template.

Create a game with a platform template:

entityjs new mygame platform

See all available templates:

entityjs templates

Creating a Component

entityjs comp rock

This will create a new component called rock at scripts/rock.js and will create a test file.

entityjs comp display/hero

This will create a hero component in the directory scripts/display.

Creating a Test

entityjs test name test1 test1

Create a test in /tests/name_test.js with two test methods.

Build Game

entityjs build

This will minify all entityjs src code and game src code into one file inside /builds

Running the Game / Tests

Make sure the server is running: entityjs server

To play visit: localhost:2345

To run tests visit: localhost:2345/test

Assets are located here: localhost:2345/assets/*name

View all commands

Directory Structure

  • Assets - Contains all external assets

    • Images - Add any images here and retrieve them with re.assets.images
    • Sounds - Add any sounds and retrieve them with re.assets.sounds
  • Build - Contains built game

  • Scripts - Contains all js, coffee sources. Xml, tmx and json files will be converted into js.

    • Plugins - Contains minified scripts for plugin play.
  • Tests - Contains test files to run in QUnit

  • Styles - Contains all css to be included. Will support sass and others later on.

  • game.json - Optional, configurate scripts order, ignore certain files, etc

Short getters and setters

var tile = re.e('tile');
tile.tileX(1); //sets
tile.tileX(); //gets

Setters can even be used in attr()

tile.attr('tileX', 2); //sets

Setter with multiple parameters

tile.tile(1, 2); //sets tilex and tiley
tile.attr('tile', [1,2]); //samething

Factories in 0.4.2

All components now have a factory method which can be used to create complex entities.

.factory(function(label, click){
  this.label = label;

    this.on('click', click);

re.button("Hello", function(){
  alert(this.label+" clicked!");

//Can be overwritten using the `method` function. A singleton is created below.

    this.instance = re.e('player');
  return this.instance;

//get player

QUnit Testing

All games use QUnit for testing, its light weight and easy to use. Checkout the platform template to see some example tests.


Factories are used to easily create complex entities. During tests you may need access to a specific type of entity multiple times. Factories make it easy to create any kind of entity at anytime.

Simply create a new factories.js in the /tests directory and add something like below.

factory('enemy', function(){
  //make a custom coin = 100;
  this.state = 'idle';

  //can use normal entity methods
  this.on('update', function(){

//create new enemy entity anywhere in tests
var e = factory('enemy');
eq(e.state, 'idle') //true

//Same as...
var e = re.e('enemy'); = 100;

What if you need multiple enemy factories?

//use f for laziness
f('enemy attacking', function(){
  this.state = 'attacking';

EntityJS Helpers

Some asserts have been added for checking entities, like expectTrigger, expectFlicker and expectListener. For more info check localhost:2345/qunit/qunit.entity.js.

Input Helpers

Special methods like keypress() and click() are available to simulate user input. Check localhost:2345/qunit/qunit.input.js for more information.

Tile Map Editor

The awesome tiled map editor is now compatible and can be used in your projects.

Simply create a new directory in /assets named levels or anything you like to save your maps in. They can accessed in code like so:

re('level1.tmx')[0]; //assuming the file name is level1.tmx
re('level'); //find all levels that are in the /assets/levels directory

If you are still confused create a new platform game and view levels are used.

Quick Start Guide

First you should install ruby and the entityjs gem.

Now you can create a new game from the platform template: entityjs new mygame platform

Move into the mygame directory and play the game: entityjs server

Open your browser and navigate to localhost:2345


Before sending a pull request it would be a good idea to run rspec and rake jasmine to make sure all tests pass in both ruby and javascript.

Running rspec will generate a /mygame/ folder with test files. It will be ignored by git so don't worry about it.