How to Debug ClojureScript

If you want to use Chrome Debugger, you can use the following...

(defn debugger []
  (js/eval "debugger"))

(debugger)

this is very much a hack, but it will active chrome's debug mode.

Remember though, Clojure Script uses namespaces, which means if you created some variable thing, then it will be found in my.namespace.thing in chrome console (as expected).

UPDATE: I've taken the liberty to change the original answer since it is so woefully out of date and I cannot unmark this answer and mark a new one.

To debug ClojureScript use source maps - https://clojurescript.org/reference/source-maps

UPDATED: Using the compiler directly is now straightforward. But lein-cljsbuild is still very useful.

Use lein-cljsbuild. You can write different builds (testing, development, release). You can auto-watch files so they recompile quickly as you change them. You can easily use browser repl to evaluate code directly in the browser. You can manage dependencies.

Specifically related to your question - lein-cljsbuild also passes along sensible warning defaults to the compiler so that you get verbose and accurate warnings before you actually run the code in the browser.

Recently (Oct. 27 2013) David Nolen released a blog post suggesting a great setup for a tight feedback loop and a good debugging experience with ClojureScript.

http://swannodette.github.io/2013/10/27/the-essence-of-clojurescript/

"This short post will get you from zero to developing source mapped ClojureScript with instant recompiles on file save."

Hope that could also help.