var canvas = document.getElementById('canvas');
if (canvas.getContext){
  var ctx = canvas.getContext('2d');

  var rectangle = new Path2D();
  rectangle.rect(10, 10, 50, 50);

  var circle = new Path2D();
  circle.moveTo(125, 35);
  circle.arc(100, 35, 25, 0, 2 * Math.PI);

  ctx.stroke(rectangle);
  ctx.fill(circle);
}