String into a javascript function call. Better way to create instance for dynamic class names

gistfile1.js

var Y = (function(){
  return  {
		Car:function(model){
			this.model = model;
			this.applyBreak = function(){
				alert("done break!!");
			}
		}
	}
})();

var json = {
	className:"Car"
}


//Solution 1 with eval - bad
 
var str = "new "+json['className']+"(2007)";
var cc = eval(str);  

//Solution 2 subscript notation -- better
function createInstance(name,param){
	return  new Y[name](param);
}
var cc = createInstance(json['className'],2007);