Directory browsing enabled flag is disabled by default. But if you enable it then the websphere application server will display the content of .war file (Excluding the WEB-INF folder) and let you browse through it.
I do have this simple WebAppExtensionSample.war file that has js folder at the root level, which has one .js file. I enabled the directory browsing and then i went to the web application context root and this is what i see
Make sure that you disable this feature before deploying your application in production
You can download the sample code from here