HTML5 Game - Velocity on two axes

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  2. HTML5 Game
  3. Canvas Animation
  4. Linear Motion

Introduction

We can define a vx and a vy.

Add the vx to the x property and the vy to the y property on each frame.

Demo

ResultView the demo in separate window 

<!doctype html>  
    <html>  
     <head>  
      <meta charset="utf-8">  
      <title>Velocity 2</title>  
      <style>canvas{border:1px solid red;}</style>  
     </head>  
     <body>  
      <canvas id="canvas" width="400" height="400"></canvas>  
      <script>  
class Ball{    /* w  ww. j a  va  2  s. co  m*/
   constructor(radius, color) {  
     if (radius === undefined) { radius = 40; }  
     if (color === undefined) { color = "#ff0000"; }  
     this.x = 0;  
     this.y = 0;  
     this.radius = radius;  
     this.rotation = 0;  
     this.scaleX = 1;  
     this.scaleY = 1;  
     this.color = color;  
     this.lineWidth = 1;  
   }  
     
   draw(context) {  
     context.save();  
     context.translate(this.x, this.y);  
     context.rotate(this.rotation);  
     context.scale(this.scaleX, this.scaleY);  
     context.lineWidth = this.lineWidth;  
     context.fillStyle = this.color;  
     context.beginPath();  
     //x, y, radius, start_angle, end_angle, anti-clockwise  
     context.arc(0, 0, this.radius, 0, (Math.PI * 2), true);  
     context.closePath();  
     context.fill();  
     if (this.lineWidth > 0) {  
       context.stroke();  
     }  
     context.restore();  
   }
}
      window.onload = function () {  
        let canvas = document.getElementById('canvas'),  
            context = canvas.getContext('2d'),  
            ball = new Ball(),  
            vx = 1,  
            vy = 1;  
      
        ball.x = 50;  
        ball.y = 100;  
      
        (function drawFrame () {  
          window.requestAnimationFrame(drawFrame, canvas);  
          context.clearRect(0, 0, canvas.width, canvas.height);  
      
          ball.x += vx;  
          ball.y += vy;  
          ball.draw(context);  
        }());  
      };  
      </script>  
     </body>  
    </html>

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