typeof null is object, not 'null'

[kahnvex]

This seems odd to me. jQuery thinks null references are type "null" (string null). But javascript's typeof thinks null references are type object.

>typeof null
'object'

Why does jQuery treat null as its own type? Treating it's "type" as an object is useful in certain cases, and since that is what the language does, this seems odd.

[scottgonzalez]

If typeof provided values we wanted, then jQuery.type() wouldn't exist. Please read the docs.

[kahnvex]

Seems odd that jQuery makes up its own types, but ok.

[rwaldron]

It's not "odd" because jQuery isn't making up it's own types: http://es5.github.io/#x8.2

typeof null === "object" began as a bug in the first implementation of JavaScript and then it stuck:

• Object type tag was 0x0: http://mxr.mozilla.org/classic/source/js/src/jsapi.h#32
• null represented by NULL pointer 0: http://mxr.mozilla.org/classic/source/js/src/jsapi.h#111
  • null incorrectly treated as having type tag 0

0x0 === 0, hence erroneous typeof result.

[timmywil]

Ok, I kind of knew this, but Rick just blew my mind.

[rwaldron]

@timmywil 😉

I just realized that I shouldn't have used === since I was talking about C code, haha

[dcherman]

@rwaldron That's pretty interesting! Out of curiosity, if this was a bug, I would have thought that there would be an ( accidentally ) unused definition for JSVAL_NULL or another condition in JS_TypeOfValue, but that may be due to my gross inexperience with C.

[rwaldron]

I think it was the logical connection of NULL pointer to null :)

Sometimes bugs, right?