js string format

/** string **/
     String.prototype.format = function(args) {
         var result = this;
         if (arguments.length > 0) {
             if (arguments.length == 1 && typeof (args) == "object") {
                 for (var key in args) {
                     if(args[key]!=undefined){
                         var reg = new RegExp("({" + key + "})", "g");
                         result = result.replace(reg, args[key]);
                     }
                 }
             }
             else {
                 for (var i = 0; i < arguments.length; i++) {
                     if (arguments[i] != undefined) {
                         var reg= new RegExp("({)" + i + "(})", "g");
                         result = result.replace(reg, arguments[i]);
                     }
                 }
             }
         }
         return result;
     }

var template1="我是{0}，今年{1}了";
 var result1=template1.format("loogn",22);

 var template2="我是{name}，今年{age}了";
 var result2=template2.format({name:"loogn",age:22});