Facade WeakMap and WeakSet

[armanbilge]

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet

Typically these collection facades are accompanied by a "wrapper" to implement Scala collection APIs e.g.

scala-js/library/src/main/scala-new-collections/scala/scalajs/js/WrappedMap.scala

Lines 22 to 26 in 2fa0a0a

	/** Wrapper to use a js.Map as a scala.mutable.Map */
	@inline
	final class WrappedMap[K, V](private val underlying: js.Map[K, V])
	extends mutable.AbstractMap[K, V]
	with mutable.MapOps[K, V, mutable.Map, js.WrappedMap[K, V]] {

However, in this case neither WeakMap nor WeakSet can fully implement any Scala collection API because they are not iterable.

So I suppose the pattern here would be to add WeakMapOps and WeakSetOps, that add Scala collections-like syntax to the facades for supported ops.