What is the ClojureScript analogue of typeof ... undefined from JavaScript? -

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i'm seeing lots of code using pattern:

if (typeof a.b === 'undefined') { ...

now i'm translating to:

(if (nil? (-.b a)) ...

is appropriate - or losing crucial data?

my question is: what clojurescript analogue of typeof ... undefined javascript?

for checking possibly undefined references can use cljs.core/exists?:

(when-not (exists? js/unknownreference)   ...)

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