Surefire Type Detection

types.js

var typs = {};

(function (self) {
     var values = [
               'Function',
               'Object',
               'Array',
               'String',
               'Number',
               'Date',
               'RegExp',
               'Boolean',
               'Null',
               'Error'
          ];

     for (var i in values) if (values.hasOwnProperty(i)) {
          var value = values[i];

          self['is' + value] = (function (v) {
               return function (o) {
                      var r = '';

                      try {
                          r = (o === null) ?
                                   'Null' :
                                   Object
                                       .prototype
                                       .toString
                                       .call(o)
                                       .replace(/^\[object\s(\w+)\]$/, '$1');
                      } catch (e) {
                          r = 'Undefined';
                      }

                      return !!(r === v);
               };
          })(value);
     }
})(typs);

alert(typs.isFunction(Object)); // --> true