js中的string.format函数代码

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

String.format = function() {
  for (var a = arguments[0], b = 1; b < arguments.length; b++) a = a.replace(RegExp("\\{" + (b - 1) + "\\}", "ig"), arguments[b]);
  return a
};