es-iterator-helpers
An ESnext spec-compliant iterator helpers shim/polyfill/replacement that works as far down as ES3.
set.prototype.difference
An ESnext spec-compliant `Set.prototype.difference` shim/polyfill/replacement that works as far down as ES3
set.prototype.union
An ESnext spec-compliant `Set.prototype.union` shim/polyfill/replacement that works as far down as ES3