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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?
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A variable that has not been assigned a value is of type undefined . A method or statement also returns undefined if the variable that is being evaluated does not have an assigned value. A function returns undefined if a value was not returned .
The typeof undefined is the string "undefined" — and undefined is a falsy value that is loosely equal to null but not to other falsy values.
variable === undefined VS typeof variable === “undefined” Here the assigned variables don't have any value but the variable exists. Here the type of variable is undefined.
For checking for possibly undefined references you can use cljs.core/exists?:
(when-not (exists? js/unknownReference)
...)
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