While the lists aspire to be exhaustive, language is far too squishy for that. As such, contributions are welcome, encouraged, and occasionally begged for.
npm install fwords
fwords is just an object with keys for each supported language (as a two-character code like "en" for English), and therein, keys for each functional category. Specifically:
aux: auxiliary verbs
require('fwords') (fwords) -> console.log fwords.en.aux > ['be able to', 'can', 'could', 'dare', 'had better', 'have to', 'may', 'might', 'must', 'need to', 'ought', 'ought to', 'shall', 'should', 'used to', 'will', 'would'] console.log fwords.total('en').length > 342
Thanks to the efforts of Leah Gilner and Franc Morales at Sequence Publishing for listing English function words! N.B. I did some minor editing to help machines parse the lists more easily, ex: "1, 2, 3, 4, etc." -> "\d+"