GZIP is not working for all files in Tomcat 7

Issue

Compression is working for most files, but there are files with Content-Type=application/javascript that are sent uncompressed. In the server.xml, compression is set to on:

    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="10000"
               compression="on" 
               compressionMinSize="1024" 
               compressableMimeType="text/html,text/xml,text/css,text/javascript,application/javascript"
               redirectPort="8443" />