HTML5 Game - Canvas Animation Spring

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Description

Spring

Demo

ResultView the demo in separate window 

<!doctype html>  
<html>  
 <head>  
  <meta charset="utf-8">  
  <title>Spring 1</title>  
  <style>canvas{border:1px solid red;}</style>  
 </head>  // ww w.j a  v  a 2  s  .  c  o  m
 <body>  
 <p>move mouse to see the result.</p>
  <canvas id="canvas" width="400" height="400"></canvas>  
  <script>  
class Ball {  
constructor() {
     this.radius = 4;
       
     this.x = 0;  
     this.y = 0;  
     this.vx = 0;  
     this.vy = 0;  
     this.rotation = 0;  
     this.scaleX = 1;  
     this.scaleY = 1;  
     this.color = "#ff0000";
     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();  
     context.arc(0, 0, this.radius, 0, (Math.PI * 2), true);  
     context.closePath();  
  context.fill();  
  if (this.lineWidth > 0) {  
    context.stroke();  
  }  
  context.restore();  
}
getBounds() {  
  return {  
    x: this.x - this.radius,  
    y: this.y - this.radius,  
    width: this.radius * 2,  
    height: this.radius * 2  
  };  
}

}  
  window.onload = function () {  
    let canvas = document.getElementById('canvas'),  
        context = canvas.getContext('2d'),  
        ball = new Ball(),  
        spring = 0.03,  
        targetX = canvas.width / 2,  
        vx = 0;  
  
    ball.y = canvas.height / 2;  
  
   let friction = 0.95;  

     
   (function drawFrame () {  
     window.requestAnimationFrame(drawFrame, canvas);  
     context.clearRect(0, 0, canvas.width, canvas.height);  
     
     let dx = targetX - ball.x,  
         ax = dx * spring;  
     
     vx += ax;  
     vx *= friction;  
     ball.x += vx;  
        if (Math.abs(vx) > 0.001) {  
     vx += ax;  
     vx *= friction;  
     ball.x += vx;  
   }  


     ball.draw(context);  
   }());  
     };  
     
     
     </script>  
    </body>  
   </html>

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