Use bigint for place values to be more adaptable with longer inputs.

Put functions with different purposes into their own files.

Use appropriate place instead of smallest group when creating placeholder groups between actual groups.

Make group management more readable.

Formal English hyphenates tens names.

Address errors with gapped groups.

Ensure digits parse correctly when there are gaps.

Make code more cleaner when parsing.

Format more sections of the code.

Include parse and stringify functions for American short-count locale.