ClojureScript: How to add method via prototype to JS Object?

Question

I'm trying to add some functionality to an existing JavaScript system. To be then used from JavaScript again (as opposed to within the ClojureScript namespace). Perhaps this isn't possible?

Here's a simplification of what I want to do:

// JavaScript
String.prototype.foo = function() {
  return "bar";
}

# CoffeeScript
String::foo = ->
  "bar"

I want to be able to run my script above, and then call it from elsewhere in the code.

I've tried messing with extend-type and defprotocol, along with export, but nothing seemed to expose my foo function.

It's possible that this was a design decision and ClojureScript isn't going to work for me here, but I just wanted to make sure I wasn't overlooking something.

dnolen · Accepted Answer · 2012-09-14 17:15:26Z

12

It can be done like so:

(set! (.-foo (.-prototype js/String)) (fn [] "bar"))

Or you can use .. sugar:

(set! (.. js/String -prototype -foo) (fn [] "bar"))

edited Sep 14, 2012 at 17:15

answered Sep 14, 2012 at 16:44

dnolen

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5 Comments

Eve Freeman Over a year ago

Tested and works. If only that were in some documentation somewhere. :)

dnolen Over a year ago

Yes someone needs to put together a ClojureScript page for common JavaScript interop forms.

Eve Freeman Over a year ago

Can you explain what some of that does--the .. is confusing. Does that just bring you out of the namespace?

dnolen Over a year ago

No it's just sugar for deep property access.

Jon Rose Over a year ago

I came across appletree.or.kr/quick_reference_cards/Others/… which has some helpful interop and general cljs forms.

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