什么是类型的ClojureScript模拟...来自JavaScript的未定义？

Question

I'm seeing lots of code using the pattern:

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

Now I'm translating this to:

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

Is that appropriate - or am I losing some crucial data?

My question is: What is the ClojureScript analogue of typeof ... undefined from JavaScript?

Answer 1

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

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