[rShergold]

yeah it's called Tree Shaking. It's been a massive area of improvement over the last few years. However JavaScript being dynamic can be very difficult to effectively statically analyse.

A good example: There is a library called Moment for handling dates. Due to the way the interface was built it basically can't be tree shaken. It's an excellent library but it's on the heavy side. For a while now people have been moving to libraries like Date-Fns which are collections of individual functions. This library can be tree shaken as it's obvious which functions you are using and which you are not