cool stuff

[xenoterracide]

shouldn't the Tree class implement the typescript Iterable<T> interface? also have you considered giving more conventional methods that mimic javascripts Set and Map so that users are generally already familiar with the API. Also (and this is my opinion, that JS should have done this for set), maybe all the extra methods like .map, .filter, .foreach from array, for set. Lastly, it'd be cool if you could add optional constructor methods

new TreeSet([ 'a', 'c', 'x', 'y'] ) // Set Takes an Iterable
new TreeMap([['key', 'value'],['nextkey', 'value]]) // takes an array of tuple? key value pairs.