I agree with you but there are ways to perform union and intersection with existing APIs. http://2ality.com/2015/01/es6-set-operations.html http://2ality.com/2

I agree with you but there are ways to perform union and intersection with existing APIs. http://2ality.com/2015/01/es6-set-operations.html http://2ality.com/2015/01/es6-set-operations.html > Long-term, I expect JavaScript to have built-in functionality for this, e.g. via functions that operate on iterables