CLJS: undefined and nil are "equally" nil?

[Frank Siebenlist]

ClojureScript:cljs.user> (def a nil)
nil
ClojureScript:cljs.user> (def b)

ClojureScript:cljs.user> (undefined? a)
false
ClojureScript:cljs.user> (undefined? b)
true
ClojureScript:cljs.user> (nil? a)
true
ClojureScript:cljs.user> (nil? b)
true
ClojureScript:cljs.user> (type a)
nil
ClojureScript:cljs.user> (type b)
nil
ClojureScript:cljs.user> (goog.typeOf a)
"null"
ClojureScript:cljs.user> (goog.typeOf b)
"undefined"
ClojureScript:cljs.user> (= a b)
true


That doesn't feel right… does it?

Definitely different from clojure… although it's difficult to compare without vars in cljs.

-FrankS.

[David Nolen]

This behavior is desirable. Unless you are in some dark cave of interop you shouldn't care.

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[Frank Siebenlist]

ClojureScript:cljs.user> (def a nil)
nil
ClojureScript:cljs.user> (def b)

ClojureScript:cljs.user> (= a b)
true
--------
user=> (def a nil)
#'user/a
user=> (def b)
#'user/b
user=> (= a b)
false
--------

I didn't realize that the above is dark cave material ;-)

Could you elaborate a little on the desirable aspect?
(I'm not arguing - only trying to understand as I have just been bitten by this behavior)

Thanks, FrankS.

[Jordan Berg]

I find this to be useful:

cljs.user> (nil? (.-key (js-obj)))

true

I like not having to use undefined? for this

[David Nolen]

This is an unrelated issue. We could probably simulate this by creating a Unbound type and initializing def'ed vars without init expressions to instances of it.

David

[Frank Siebenlist]

I opened issue CLJS-457 for this enhancement/bug.

As a workaround, one can test for undefined?, although that is not really the same and cljs-specific, but for my use case that will do.

Thanks, Frank.

[David Nolen]

Thanks, will look into it.