ClojureScript to check if a property exists in a js object

Question

How do I write the following in clojurescript?

obj = {"a" : 4};
"a" in obj;

did you see https://himera.herokuapp.com/synonym.html ? – edbond Feb 26 '14 at 16:43 — edbond, Feb 26 '14 at 16:43
This works too: `(js* "'a' in obj")`. But thats cheating ;) – bluegray Feb 28 '14 at 14:37 — bluegray, Feb 28 '14 at 14:37
usage of js* is a bad practice, try to not use it – edbond Feb 28 '14 at 17:03 — edbond, Feb 28 '14 at 17:03

score 11 · Answer 1 · answered Aug 18 '15 at 21:02

exists? was added to check for undefined in ClojureScript :

   (ns my.ns
     (:require-macros [cljs.core :refer [exists?]]))

   (if (exists? js/jQuery)
      (println "jQuery"))
      (println "no jQuery"))

One can also use aget and nil? to avoid calling JavaScript functions :

(def scope (js-obj))
(aset scope "var1" "Value")
(aget scope "var1")               ;; "Value"
(aget scope "anotherVar")         ;; nil
(nil? (aget scope "anotherVar"))  ;; true

score 7 · Accepted Answer · edited May 23 '17 at 12:25

7

Following the accepted SO way to check if a js object property exists using the method "hasOwnProperty" We can translate it as follows:

(def foo (js-obj "bar" "baz"))
(.hasOwnProperty foo "bar")
;; => true
(.-bar foo)
;;=> "baz"
(.hasOwnProperty foo "car")
=> false
(.-car foo)
;;=> nil

edited May 23 '17 at 12:25

Community

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answered Feb 27 '14 at 11:47

tangrammer

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ClojureScript to check if a property exists in a js object

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