I'm trying to create a simple app that draws rectangles within the Canvas tag. I've got the Canvas resizing to fullscreen, but whenever I resize the viewport, Canvas clears. I'm trying to prevent it from clearing and just keeping the content that's within it. Any ideas?

http://mediajux.com/experiments/canvas/drawing/

  /*

  * This is the primary class used for the application

  * @author Alvin Crespo

  */

  var app = (function(){



    var domBod          = document.body;

    var canvas          = null;

    var canvasWidth     = null;

    var canvasHeight     = null;

  

    return {



      //Runs after the DOM has achieved an onreadystatechange of "complete"

      initApplication: function()

      {

        //setup envrionment variables

        canvas = document.getElementById('canvas') || null;

  

        //we need to resize the canvas at the start of the app to be the full window

        this.windowResized();

  

        //only set the canvas height and width if it is not false/null

        if(canvas)

        {

          canvasWidth = canvas.offsetWidth;

          canvasHeight = canvas.offsetHeight;        

        }

  

        //add window events

        window.onresize = this.windowResized;   

  

        circles.canvas = canvas;

        circles.canvasWidth = canvasWidth;

        circles.canvasHeight = canvasHeight;

        circles.generateCircles(10);  

  

        setInterval(function(){

            circles.animateCircles();

        }, 50);   

      },



      /**

      * Executes Resizing procedures on the canvas element

      */

      windowResized: function()

      {

        (this.domBod === null) ? 'true' : 'false';

        try{

          console.log(canvas);

          canvas.setAttribute('width', document.body.clientWidth);

          canvas.setAttribute('height', document.body.clientHeight);        

        }catch(e) {

          console.log(e.name + " :: " + e.message);

        }

      },



      /**

      * Returns the canvas element 

      * @returns canvas

      */

      getCanvas: function()

      {

        return canvas;

      }



    };

  })();