The global object in javascript

Question

If I run this code in chrome:

for(var i in window){console.log(i)}

I get a lot of properties as shown below.

But if I run this code:

console.log(window.hasOwnProperty("parseInt"))
console.log(window.hasOwnProperty("undefined"))

I get true for both.

How is it possible that .hasOwnProperty() returns true, yet it doesn't show up in the list of properties produced by the for-in loop?

Result from loop:

top VM1531:2
window VM1531:2
location VM1531:2
external VM1531:2
chrome VM1531:2
document VM1531:2
getInnerFunction VM1531:2
theInnerFunction VM1531:2
__commandLineAPI VM1531:2
i VM1531:2
speechSynthesis VM1531:2
localStorage VM1531:2
sessionStorage VM1531:2
applicationCache VM1531:2
webkitStorageInfo VM1531:2
indexedDB VM1531:2
webkitIndexedDB VM1531:2
crypto VM1531:2
CSS VM1531:2
performance VM1531:2
console VM1531:2
devicePixelRatio VM1531:2
styleMedia VM1531:2
parent VM1531:2
opener VM1531:2
frames VM1531:2
self VM1531:2
defaultstatus VM1531:2
defaultStatus VM1531:2
status VM1531:2
name VM1531:2
length VM1531:2
closed VM1531:2
pageYOffset VM1531:2
pageXOffset VM1531:2
scrollY VM1531:2
scrollX VM1531:2
screenTop VM1531:2
screenLeft VM1531:2
screenY VM1531:2
screenX VM1531:2
innerWidth VM1531:2
innerHeight VM1531:2
outerWidth VM1531:2
outerHeight VM1531:2
offscreenBuffering VM1531:2
frameElement VM1531:2
clientInformation VM1531:2
navigator VM1531:2
toolbar VM1531:2
statusbar VM1531:2
scrollbars VM1531:2
personalbar VM1531:2
menubar VM1531:2
locationbar VM1531:2
history VM1531:2
screen VM1531:2
postMessage VM1531:2
close VM1531:2
blur VM1531:2
focus VM1531:2
ondeviceorientation VM1531:2
ondevicemotion VM1531:2
onautocompleteerror VM1531:2
onautocomplete VM1531:2
onunload VM1531:2
onstorage VM1531:2
onpopstate VM1531:2
onpageshow VM1531:2
onpagehide VM1531:2
ononline VM1531:2
onoffline VM1531:2
onmessage VM1531:2
onhashchange VM1531:2
onbeforeunload VM1531:2
onwaiting VM1531:2
onvolumechange VM1531:2
ontoggle VM1531:2
ontimeupdate VM1531:2
onsuspend VM1531:2
onsubmit VM1531:2
onstalled VM1531:2
onshow VM1531:2
onselect VM1531:2
onseeking VM1531:2
onseeked VM1531:2
onscroll VM1531:2
onresize VM1531:2
onreset VM1531:2
onratechange VM1531:2
onprogress VM1531:2
onplaying VM1531:2
onplay VM1531:2
onpause VM1531:2
onmousewheel VM1531:2
onmouseup VM1531:2
onmouseover VM1531:2
onmouseout VM1531:2
onmousemove VM1531:2
onmouseleave VM1531:2
onmouseenter VM1531:2
onmousedown VM1531:2
onloadstart VM1531:2
onloadedmetadata VM1531:2
onloadeddata VM1531:2
onload VM1531:2
onkeyup VM1531:2
onkeypress VM1531:2
onkeydown VM1531:2
oninvalid VM1531:2
oninput VM1531:2
onfocus VM1531:2
onerror VM1531:2
onended VM1531:2
onemptied VM1531:2
ondurationchange VM1531:2
ondrop VM1531:2
ondragstart VM1531:2
ondragover VM1531:2
ondragleave VM1531:2
ondragenter VM1531:2
ondragend VM1531:2
ondrag VM1531:2
ondblclick VM1531:2
oncuechange VM1531:2
oncontextmenu VM1531:2
onclose VM1531:2
onclick VM1531:2
onchange VM1531:2
oncanplaythrough VM1531:2
oncanplay VM1531:2
oncancel VM1531:2
onblur VM1531:2
onabort VM1531:2
onwheel VM1531:2
onwebkittransitionend VM1531:2
onwebkitanimationstart VM1531:2
onwebkitanimationiteration VM1531:2
onwebkitanimationend VM1531:2
ontransitionend VM1531:2
onsearch VM1531:2
getSelection VM1531:2
print VM1531:2
stop VM1531:2
open VM1531:2
alert VM1531:2
confirm VM1531:2
prompt VM1531:2
find VM1531:2
scrollBy VM1531:2
scrollTo VM1531:2
scroll VM1531:2
moveBy VM1531:2
moveTo VM1531:2
resizeBy VM1531:2
resizeTo VM1531:2
matchMedia VM1531:2
getComputedStyle VM1531:2
getMatchedCSSRules VM1531:2
webkitConvertPointFromPageToNode VM1531:2
webkitConvertPointFromNodeToPage VM1531:2
requestAnimationFrame VM1531:2
cancelAnimationFrame VM1531:2
webkitRequestAnimationFrame VM1531:2
webkitCancelAnimationFrame VM1531:2
webkitCancelRequestAnimationFrame VM1531:2
captureEvents VM1531:2
releaseEvents VM1531:2
btoa VM1531:2
atob VM1531:2
setTimeout VM1531:2
clearTimeout VM1531:2
setInterval VM1531:2
clearInterval VM1531:2
TEMPORARY VM1531:2
PERSISTENT VM1531:2
showModalDialog VM1531:2
webkitRequestFileSystem VM1531:2
webkitResolveLocalFileSystemURL VM1531:2
openDatabase VM1531:2
addEventListener VM1531:2
removeEventListener VM1531:2
dispatchEvent

Answer 1

Object properties can be hidden from iteration mechanisms by marking them as not being "enumerable":

var foo = { a: "Hello", b: "World" };
Object.defineProperty(foo, "c", { value: "where am I?" });

By default, properties defined with defineProperty() are not enumerable, so if you ran a for ... in loop over object "foo" you wouldn't see "c".

Of course, the global object is something with all sorts of magic properties, but the basic "enumerable" flag still applies. As to why exactly "parseInt" and "undefined" are not enumerable, I have no insight.

edit — cookie monster points out in a comment that the Object.getOwnPropertyNames() function will return the names of non-enumerable properties. However Object.keys() will not. Thus you could use that difference to see whether an object has non-enumerable properties:

 function hasSneakyProperties(o) {
     return Object.getOwnPropertyNames(o).length !== Object.keys(o).length;
 }

I don't know why anybody would do that but there you go.