Creating a Rotating Shape Using Javascript

Submitted by jaredgwapo on Wednesday, January 13, 2016 - 10:27.

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In this chapter, I am going to teach you how to make a rotating image or shape using javascript. Download the source code and follow the directions below. You can use this to your simple projects.

DIRECTIONS

HTML CODE

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
 
</body>
</html>

<script>
 
var myGamePiece;
 
function startGame() {
    myGamePiece = new component(30, 30, "red", 80, 75);
    myGameArea.start();
}
 
var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 20);
    },
    stop : function() {
        clearInterval(this.interval);
    },    
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}
 
function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    this.angle = 0;
    this.x = x;
    this.y = y;    
    this.update = function() {
        ctx = myGameArea.context;
        ctx.save();
        ctx.translate(this.x, this.y);        
        ctx.rotate(this.angle);
        ctx.fillStyle = color;
        ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height);        
        ctx.restore();    
    }
}
 
function updateGameArea() {
    myGameArea.clear();
    myGamePiece.angle += 1 * Math.PI / 180;    
    myGamePiece.update();
}
 
</script>

Note: Due to the size or complexity of this submission, the author has submitted it as a .zip file to shorten your download time. After downloading it, you will need a program like Winzip to decompress it.

Virus note: All files are scanned once-a-day by SourceCodester.com for viruses, but new viruses come out every day, so no prevention program can catch 100% of them.

FOR YOUR OWN SAFETY, PLEASE:

1. Re-scan downloaded files using your personal virus checker before using it.
2. NEVER, EVER run compiled files (.exe's, .ocx's, .dll's etc.)--only run source code.

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