Use apply on native JavaScript functions

Question

In clojureScript the following multi-arity function

(defn sum [& xs] (reduce + xs))

can be either called via (sum 4 6 9) or by the use of (apply sum [4 6 9]) which yields the same result.

How can this be done with a native JavaScript function, such as: console.log.

(apply js/console.log [1 2 3])

This, yields the following error:

#object[TypeError TypeError: 'log' called on an object that does not implement interface Console.]

Hyalite

I'm not sure about clojureScript, but in JS you need console.log.apply(console, […]) to make it work (though it's browser-specific) – Minstrel

hmm... this is interesting. In planck (osx clojurescript repl) I tried this out and it worked fine. (apply js/console.log [1 2 3]) and (js/console.log 1 2 3) both print 1 and return nil – Alert

this has gotta be some browser-specific thing. I just fired up a minimal figwheel project (from this template: github.com/bhauman/figwheel-template ) and sent (apply js/console.log [1 2 3]) to the browser from the figwheel repl; it logged 1 2 3 --- I'm using a current version of Chrome, what are you using? – Alert

just to make sure this isn't an implementation difference on the javascript side in whatever environment you're using, what happens when you try (apply js/Math.sqrt [25])? It should return 5 without a problem. – Alert

Answer 1

Some browsers always assuming the this is certain object, you can use .bind in js for temporal fix.

; you can use .bind on any function
(def d (.bind (.-log js/console) js/console))
(def ms ["aaa" "bbb" "barbarbar"])
(mapv d ms)

Related questions

What does this statement do? console.log.bind(console)

Why do js functions fail when I assign them to a local variable?

Wooer

Answer 2

There might be an error in your code. apply works totally fine out of the box for JS functions:

cljs.user=> (apply js/Math.sqrt [25])
5

You can test it with this online REPL and I also tested it in my local project -- no problems so far.

cljs.user=> (apply js/console.log [1 2 3])
nil

also prints the output in the normal JS console as expected.

Gnathion

Answer 3

Using js/a.b only works when a is global in your environment. Either way, I find this much cleaner:

(apply (.-log js/console) [1 2 3])

Note: with member functions, don't forget the first argument is this.

Decoration