Check for NaN in ClojureScript

Question

How can I check if a value is NaN? I'd prefer a solution that can be used in Clojure too without much extra stuff (so I don't want to use an external library, such as underscore). Here is what I tried

(number? js/NaN) ;=> true, well I'd expect false
(= js/NaN (js/parseInt "xx")) ;=> false
(= js/NaN js/NaN) ;=> false, even worse

; This is the best I could come up with
(defn actual-number? 
  [n] 
  (or (> 0 n) (<= 0 n)))

score 23 · Accepted Answer · answered Jun 07 '13 at 12:19

23

You shouldn't compare NaN's - they're always unequal. You should be able to use javascript's built-in isNaN function like

(js/isNaN x)

answered Jun 07 '13 at 12:19

Joost Diepenmaat

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Note that the `js/isNaN` function doesn't exist in IE11. I've just hit this problem! – Scott Jan 23 '19 at 18:05

score 3 · Answer 2 · answered Jun 07 '13 at 12:20

3

You can use isNaN js function:

(js/isNaN ..)

answered Jun 07 '13 at 12:20

Ankur

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Beware: `js/isNaN` doesn't exist in IE11. – Scott Jan 23 '19 at 18:05

score 2 · Answer 3 · answered Aug 24 '13 at 15:11

Be aware that

(js/isNaN [1,2])

returns true. There are other many cases where js/isNaN does not correspond to what one expects.

If you're using underscore.js in the browser, you can delegate to (.isNaN js/_ ..) instead.

Otherwise, the following function should to the trick:

(defn isNaN [node]
  (and (= (.call js/toString node) (str "[object Number]"))
       (js/eval (str node " != +" node ))))

Check for NaN in ClojureScript

3 Answers3