Is there a simple way to list the properties and functions of a JavaScript object in ClojureScript?
I've tried the following:
(keys (js->clj (.getContext canvas "2d")))
But this throws the following error:
ExceptionInfo #<Error: [object CanvasRenderingContext2D] is not ISeqable> clojure.core/ex-info (core.clj:4591)
I figured out a way. You can just call
(js-keys (.getContext canvas "2d"))
and that will list all functions and properties of the JavaScript object.
You are calling keys clojure function, which returns keys of a (clojure) map. To return all properties of javascript object you should do this :
(.keys js/Object myObject)
which is the analogy of javascript code :
Object.keys(myObject);
Edit : I just looked into the source of js->clj - https://github.com/clojure/clojurescript/blob/master/src/main/cljs/cljs/core.cljs and I also tried it with canvas context. The problem is that the canvas context isn't a standard js/Object and therefore condition (identical? (type x) js/Object) is not satisfied and the js->clj function ends up in the else branch, which makes js->clj behave as identity function, which means that it just returns the context as you pass it in.
This is the source code :
(defprotocol IEncodeClojure
(-js->clj [x options] "Transforms JavaScript values to Clojure"))
(defn js->clj
"Recursively transforms JavaScript arrays into ClojureScript
vectors, and JavaScript objects into ClojureScript maps. With
option ':keywordize-keys true' will convert object fields from
strings to keywords."
([x] (js->clj x {:keywordize-keys false}))
([x & opts]
(let [{:keys [keywordize-keys]} opts
keyfn (if keywordize-keys keyword str)
f (fn thisfn [x]
(cond
(satisfies? IEncodeClojure x)
(-js->clj x (apply array-map opts))
(seq? x)
(doall (map thisfn x))
(coll? x)
(into (empty x) (map thisfn x))
(array? x)
(vec (map thisfn x))
(identical? (type x) js/Object)
(into {} (for [k (js-keys x)]
[(keyfn k) (thisfn (aget x k))]))
:else x))]
(f x))))
goog.object.getKeys.
