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Asked: 2026-06-01T02:13:20+00:00

According to the documentation here: https://github.com/playframework/Play20/wiki/AssetsGoogleClosureCompiler it says: Any JavaScript file present in app/assets

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According to the documentation here: https://github.com/playframework/Play20/wiki/AssetsGoogleClosureCompiler it says:

Any JavaScript file present in app/assets will be parsed by Google Closure compiler, checked for errors and dependencies and minified if activated in the build configuration.

However I can’t find out how to set this in the build configuration, I tried adding the code:

val main = PlayProject(appName, appVersion, mainLang = SCALA).settings(
    javascriptEntryPoints <<= baseDirectory(base =>
        base / "app" / "assets" / "javascripts" ** "*.js"
    )
)

in build.scala however I can’t find any minified JavaScript files.

Here are the steps I’ve tried:

  1. Add the above code in build.scala

  2. Create a JavaScript file in app/assets/javascripts

  3. Type “compile” in the Play console and notice that no minified JavaScript files are produced in app/assets/javascripts or public/javascripts

However, I have noticed that if I write some invalid JavaScript, I’ll get an error message (e.g. on 127.0.0.1:9000 – Compilation error) so it looks like closure compiler is checking for errors successfully, however I’m not sure how to do the minification.

While on the subject of minification, is it possible to use the regular (non-minified) JavaScript file only in development mode, but in production, use the minified version?

Thanks

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1 Answer

  1. Editorial Team

    Play does not put the assets into public or the assets folder after they have been compiled. The compiled assets (JS, Less or CoffeeScript) get placed inside:

    /target/scala[version]/resource_managed/main/…

    Play will then create a mapping to these files so that you can treat the assets as if they did live in the /public folder.

    One thing to note is that during development mode compile will not output the files into this directory. When you hit your localhost:9000 path with the browser, this will do the final compile and then output the files to the directory.

    To answer the minified version (and to see a better example of how to change the build config), I recommend checking out Yann Simon’s post on using Less in Play. It’s conceptually the same process as JS and he also has a great example on how to switch between un-minified/minified versions based on the Play mode:

    https://plus.google.com/u/0/108788785914419775677/posts/QgyUF9cXPkv

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