Problem with file watcher (file not found)

I can run uglifyjs from a terminal and it works fine, as seen here:

However, when I set up a file watcher to try to duplicate this I keep getting the error "An exception occurred while executing watcher 'uglifyjs'. Watcher has been disabled. Fix it.: Cannot run program "uglifyjs" (in directory "D:\projects\HUDD"): CreateProcess error=2, The system cannot find the file specified".

Here is my watcher:

What am I doing wrong?