Javascript String Format fix

String.prototype.format = String.prototype.f = function() {
    var s = this,
        i = arguments.length;
        var compareStr = '';
        var map = {};
    if ( (arguments.length == 1) && (typeof arguments[0] === 'object')) {
      for (var prop in arguments[0]) {
            key = prop;
            compareStr += key+'|';
            map['{'+key+'}'] = arguments[0][prop];
      }
    } else {
      while (i--) {
          key = i;
          compareStr += key+'|'; 
          map['{'+key+'}'] = arguments[i];
      }
    }

   var regExp = new RegExp("{("+compareStr+")}", "g");
     s = s.replace(regExp, function (matched){
        return map[matched];
    });
  
    return s;
};



var test = "Hello {name}, {world}";
var test2 =" Hello {0}, {1}";
console.log(test.format({"name":"A", "world" : "B"}));
console.log(test2.format("C","D"));