gistfile1.js

var rectangle = { x     : 0
                , y     : 0
                , w     : 10
                , h     : 10
                , color : '#ff9900' }

  , drawRec = function(recObj, modifyColor) {
      
      // do some canvas setup stuff, then set the fill color...
      if (modifyColor === 'undefined'){
        canvasContext.fillStyle = recObj.color;
      }
      else {
        canvasContext.fillStyle = '#999999'
      }

      // draw some stuff
    }