console 命令行工具 X clear

console

function Ball(radius,color){
    if(!radius){
        radius=40;
    }

    if(!color){
        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;

}

Ball.prototype.draw=function(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,0,2*Math.PI,true)
    context.closePath()
    context.fill()

    context.restore()
}
 
var canvas=document.getElementById("canvas")
var ctx=canvas.getContext("2d")
var ball=new Ball(10)
ball.draw(ctx)

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=, initial-scale=">
	<meta http-equiv="X-UA-Compatible" content="">
	<title></title>
</head>
<body>
	<canvas id="canvas"></canvas>

    <!-- <script src="//jsrun.net/FavKp.js"></script> -->
</body>
</html>