npm needs to learn how to deal with that. For example, if a package is marked as requiring 5.4, but you have 4.2, then it should automatically use a tool like babel to convert unavailable ES6 syntax to ES5 for compatibility. I really want to be able to write my modules to take advantage of ES6 while not having to build all that babel stuff into my module for compatibility.
Some of that is possible, but some of that is not. Consider the use case of WeakMaps or Proxies that cannot truly be polyfilled, they need to be implemented at the language level.
Suppose you could transpile what is possible, then throw errors otherwise, however that would involve parsing each file in an NPM module which is probably an unreasonable task performance wise.
