Compare two directories with files names and return new files

Is there any way in angular or through grunt to compare two directories of files with file names and return/write new file names to a text or json file

The issue names Angular and Grunt but no repository files, entry points, or tests. Start by determining whether this belongs as a Grunt task and clarifying how the two directories should be compared and whether output should be text or JSON. Done would mean an agreed comparison behavior and an implemented, tested result.

Written by the indexing model from the issue text.