Sharing simple examples of HTML5 object-oriented game development

I found a good example while reading a HTML5 related book on game development. Through this example, I can have a deeper understanding of object-oriented development. What this object wants to achieve is: drawing an image in a CSS sprite into canvas. First create a SpriteSheet object, the code is as follows:

var SpriteSheet = new function(){
	this.map = { };
	this.load = function(spriteData,callback){
		this.image = new Image();
		this.image.onload = callback;
		this.image.src = "images/sprites.png";
	};
	this.draw = function(ctx,sprite,x,y,frame){
		var s = this.map[sprite];
		if (!frame) {
			frame = 0;
		};
		ctx.drawImage(this.image, s.sx+frame*s.w, s.sy, s.w, s.h, x, y, s.w, s.h);
	};
}

First use new function(){} to ensure that only one instance will be created.

Next, inside the object, two methods and a property are bound to it through this. The load method plays the role of loading the image and passes two parameters. The first parameter is the image information, that is, the position and size of the image to be drawn in the sprite and the position and size on the canvas. Pay attention to the usage of callback. This.image.onload = callbak; when the image is loaded, the passed in callback function is executed.

The draw method is used to draw images, passing in the context of the canvas, the image object information that needs to be drawn, and the image position.

The logical structure of this object is relatively complex. The basic idea is to customize the load method and complete the loading of image information through the load method. The image information here refers to the position, size, etc. of the image in the sprite.

The method code for using this object is as follows:

function startGame(){
	SpriteSheet.load({
		ship:{sx:0, sy:0, w:18, h:35, frames:3}
	},function(){
		SpriteSheet.draw(ctx,"ship",0,0);
		SpriteSheet.draw(ctx,"ship",100,50);
		SpriteSheet.draw(ctx,"ship",150,100,1);
	});
}

The load method is used here. First, the relevant data of the required cutting part is passed in, and then the draw method of the object is called in the callback function. Image drawing.

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