viewmodel

  
function ViewModel(rootElement){
  
  rootElement = rootElement || document;
  
  var model = Object.create(null);

  function updateElement(elm){ 
	  var key  = elm.getAttribute("bind"),
		  pre  = elm.getAttribute("pre") || "",
		  post = elm.getAttribute("append") || "",
		  prop = elm.getAttribute("prop") || "innerHTML";
	  requestAnimationFrame(function(){
			elm[prop] = unescape(pre) + model[key] + unescape(post);
	  });
  }

  model.set = function(k, v) {
	  if(model[k]===v) return;
	  model[k]=v;
	  [].forEach.call(rootElement.querySelectorAll("[bind='"+k+"']"), updateElement );  
	  return model;
  };

  model.update = function(obj) {
	  Object.keys(obj).forEach(function(k,i,r) {
		  model.set(k, obj[k]);
	  });
	  return model;
  };
  
  return model;
} // end ViewModel()