create many items from an array to canvas
function ball(){
this.x = Math.random() * 100;
this.y = Math.random() * 100;
this.radius = Math.random() * 10;
this.color = "#" + (Math.random() * 16777215).toString(16);
this.draw = function(){
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, 2*Math.PI, false);
ctx.fillStyle = color;
ctx.fill();
ctx.closePath();
}
}
var balls = [];
for(var i = 0; i < 4; i++) {
balls[i] = new ball();
balls[i].draw();
}