Takes two argument, self and other, and returns a boolean indicating if all the elements in self are also contained within other.
self
other
If Set.isSubsetOf() is not supported then a polyfill will be used.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/isSubsetOf
Takes two argument,
selfandother, and returns a boolean indicating if all the elements inselfare also contained withinother.If Set.isSubsetOf() is not supported then a polyfill will be used.