Exploring JavaScript Game Engines: Impact.js, Babylon.js, and Cocos2d-js

JavaScript has become a popular choice for game development due to its versatility and wide adoption across different platforms. To facilitate game development, several JavaScript game engines have emerged, each with its own set of features and capabilities. In this article, we will explore three popular JavaScript game engines: Impact.js, Babylon.js, and Cocos2d-js. We will delve into the theory behind these engines, provide code examples with outputs where possible, and conclude with a comparison of their strengths and weaknesses.

Impact.js

Impact.js is a robust and well-established JavaScript game engine that focuses on 2D game development. It provides a comprehensive set of features for building games, including a powerful physics engine, sprite management, audio support, and an entity component system.

One of the key features of Impact.js is its intuitive and easy-to-use level editor, which allows developers to create and design game levels efficiently.

Example 

Let's take a look at a simple code example that demonstrates the creation of a game level using Impact.js:

// Level definition
ig.module('game.levels.level1')
   .requires('impact.image')
   .defines(function() {
      LevelLevel1 = {
         // Load the tileset
         tileset: new ig.Image('media/tiles.png'),
            
         // Define the level size and collision map
         width: 10,
         height: 10,
         data: [
            [1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 0, 0, 1, 1, 1, 1, 0, 0, 1],
            [1, 0, 0, 1, 0, 0, 1, 0, 0, 1],
            [1, 0, 0, 1, 0, 0, 1, 0, 0, 1],
            [1, 0, 0, 1, 1, 1, 1, 0, 0, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
         ]
      };
   });

Explanation

In this example, we define a game level using a 2D array, where 1 represents a solid tile and 0 represents an empty space. The defined level can be loaded and rendered using the Impact.js framework.

When using Impact.js, the expected output would be a rendered game level based on the defined tileset and collision map. The output would be a 2D representation of the level with solid tiles and empty spaces.

Babylon.js

Babylon.js is a powerful and feature-rich JavaScript game engine primarily designed for 3D game development. It provides a wide range of tools and functionalities, including a flexible rendering pipeline, physics simulation, animation support, and a scene graph management system.

One of the standout features of Babylon.js is its ability to handle complex 3D scenes with ease. Let's take a look at a code example that demonstrates the creation of a basic 3D scene using Babylon.js −

Example 

// Initialize the Babylon.js engine
var canvas = document.getElementById("renderCanvas");
var engine = new BABYLON.Engine(canvas, true);

// Create a scene
var scene = new BABYLON.Scene(engine);

// Create a camera
var camera = new BABYLON.ArcRotateCamera("camera", 0, 0, 10, new BABYLON.Vector3(0, 0, 0), scene);
camera.attachControl(canvas, true);

// Create a light source
var light = new BABYLON.HemisphericLight("light", new BABYLON.Vector3(0, 1, 0), scene);

// Create a sphere mesh
var sphere = BABYLON.MeshBuilder.CreateSphere("sphere", { diameter: 2 }, scene);

// Run the render loop
engine.runRenderLoop(function () {
   scene.render();
});

Explanation

In this example, we initialise the Babylon.js engine, create a scene, camera, light source, and a sphere mesh. The render loop continuously updates and renders the scene, resulting in the display of the 3D objects on the canvas.

The provided code for Babylon.js creates a basic 3D scene with a camera, a light source, and a sphere mesh. When executed, the expected output would be a canvas rendering of the 3D scene with a camera perspective showing a sphere in the center of the screen, lit by the light source.

Cocos2d-js

Cocos2d-js is a JavaScript game engine that allows developers to create games for both web and mobile platforms. It provides a comprehensive set of tools and libraries for 2D game development, including sprite animation, physics simulation, audio support, and user input handling.

One of the notable features of Cocos2d-js is its cross-platform support, enabling developers to target multiple platforms with a single codebase. Let's take a look at a simple code example that demonstrates the creation of a sprite and its animation using Cocos2d-js.

Example 

// Create a sprite
var sprite = new cc.Sprite("res/sprite.png");
sprite.setPosition(cc.winSize.width / 2, cc.winSize.height / 2);
this.addChild(sprite);

// Create an animation
var animation = new cc.Animation();
animation.addSpriteFrameWithFile("res/frame1.png");
animation.addSpriteFrameWithFile("res/frame2.png");
animation.setDelayPerUnit(0.2);
animation.setRestoreOriginalFrame(true);

// Run the animation
var animateAction = new cc.Animate(animation);
sprite.runAction(new cc.RepeatForever(animateAction));

Explanation

In this example, we create a sprite object and position it at the center of the screen. We then define an animation by adding multiple sprite frames and specifying the delay between frames. Finally, we run the animation on the sprite, resulting in a smooth animation loop.

The provided code for Cocos2d-js creates a sprite and runs a simple animation on it. When executed, the expected output would be a canvas rendering of the sprite with the defined animation. In this case, the sprite would display two frames alternately (frame1.png and frame2.png) with a delay of 0.2 seconds between frames, creating a looping animation effect.

Conclusion

In conclusion, the exploration of JavaScript game engines has provided insights into three popular options: Impact.js, Babylon.js, and Cocos2djs. Each engine has its own strengths and areas of focus, catering to different game development needs.