Choosing a graphic library for jscript:

there are several options:

raphael:

http://raphaeljs.com/ Light weight and highly compatible crossbrowsers.

paper.js:

http://paperjs.org/ Looks really powerfull

Fabric.js:

http://fabricjs.com/

Faster than raphael and supports touch devices. Sample html with fabrik:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <script src="https://rawgit.com/kangax/fabric.js/master/dist/fabric.js"></script>
  </head>
  <body>
    <canvas id="c" width="300" height="300" style="border:1px solid #ccc"></canvas>
    <script>
      (function() {

        var canvas = new fabric.Canvas('c');

      })();
    </script>
  </body>
</html>