what is "js/" in clojurescript?

[Rob]

Hi,

Syntax like this doesn't work in normal Clojure, right?

    js/document.body.style

It just did in a ClojureScript repl.  Is there something magic about "js/" ?  What is it?

thanks,

Rob

[Tamreen Khan]

A quick explanation is that functions/other javascript objects that otherwise exist in the global namespace (ie. document, console, window) are accessed through the js/ in Clojurescript. This is a JS-specific thing and therefore you don't find js/ in regular Clojure.

However, doing the form (MyClass/MyStaticMethod arg1 arg2 ...) *does* exist in Clojure. It's a way of calling static Java methods or accessing static fields. See  http://clojure.org/java_interop for more info.

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[Rob]

On Thursday, May 3, 2012 12:17:03 AM UTC-4, Tamreen Khan (Scriptor) wrote:

However, doing the form (MyClass/MyStaticMethod arg1 arg2 ...) *does* exist in Clojure. It's a way of calling static Java methods or accessing static fields. See  http://clojure.org/java_interop for more info.

Okay.  It seems like normal Clojure the thing after the slash can't have more '.' characters in it, so I'm wondering if that's the extend of the difference.  Maybe that difference is not on purpose.

[David Nolen]

I would not rely on this behavior. Follow Clojure's property access conventions.

David 

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[Devin Walters]

Some additional information if you're interested:
http://dev.clojure.org/jira/browse/CLJS-89
http://dev.clojure.org/display/design/Unified+ClojureScript+and+Clojure+field+access+syntax

'(Devin Walters)

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[Peter Taoussanis]

> I would not rely on this behavior. Follow Clojure's property access conventions.

Sorry to dig this up again - would just like to clarify:

The idiomatic way of accessing something like `window.location.pathname` then would be (aget js/window "location" "pathname"), or nested .- accesses, correct? I know things with Cljs are developing quickly and I keep seeing the `js/window.location.pathname` form pop up (including in Clojurescript's samples/twitterbuzz/src/twitterbuzz/anneal.cljs), so just wanted to double check.

Assuming the latter form is indeed incorrect, any chance of adding a compiler warning to start dissuading people from using it?

Thanks!

[David Nolen]

Yes a warning would be great as well as fixing the examples.

Ticket & patch welcome.

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[Peter Taoussanis]

Thanks David.

Ticket & patch welcome.

I've been lazy / holding out for the electronic CA, but I'll make a note to come back to this if no one else steps up.

Cheers!

[Jonas]

Hi

I created an issue+patch on JIRA: http://dev.clojure.org/jira/browse/CLJS-455

Jonas

[David Nolen]

Thanks!

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[Roberto Agostino Vitillo]

As noted in the BR, it seems like JS style access after the / was actually intended. Is this behaviour documented somewhere? I see more and more examples in the wild that exploit this feature, it would be great to have it documented somewhere as it can cause confusion.