Not sure if this is right - see https://github.com/edx/edx-platform/blob/master/docs/en_us/developers/source/i18n.rst#javascript-files

Have you tried doing the dummy translation and seeing if this works? See https://github.com/edx/edx-platform/blob/master/docs/en_us/developers/source/i18n.rst#building-and-testing-your-code