Is every JavaScript Object a function?

Question

Is there a JavaScript Object that is not a function?

javascript: x=y=z=Object; alert([window.navigator.userAgent,x,y,z].join(\"\\n\\n\"))

(

Answer 1

Here is a surefire way to check the type of anything in js.

note: you should send in something other than window...

try it out here...

            (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);
                }
           })(window);

           alert(isFunction(Object));

Answer 2

Any function can be used as a constructor to create an object by using the new operator before the function name in JavaScript. The resulting object will not be a Function.

There is also a circular relationship between Object and Function that can be tested with:

Object instanceof Function // true
Function instanceof Object // true

And {} and Object are not the same, but {} and new Object() are.

function foo() {}
foo instanceof Function // true
foo instanceof Object // true

var bar = new foo();
bar instanceof Function // false
bar instanceof Object // true

var baz = {};
baz instanceof Function; // false
baz instanceof Object; // true

Answer 3

You are assigning the Object constructor to the vars x, y and z. If you instead say x=new Object(), you will no longer see them referred to as functions.

Answer 4

You didn't create objects, you created references to the Object function. If you wanted those to be objects you could do this:

x = y = z = {}

Then alert(x) will return object [Object].

To (hopefully) encompass the comments - by default Object is a Function which constructs Objects. If you reassign the name Object (Firefox at least seems to allow me to, haven't tested all browsers) then Object will no longer be a Function, it will be whatever you assigned to it. So then, the answer is "no", Object is not always a Function, but should be unless it has been explicitly re-declared. According to Firebug:

>>> Object
Object()
>>> Object = {}
Object {}
>>> Object
Object {}

Seemingly it can be reassigned. I cannot vouch for what kind of impacts that would have, if any.