Replacing pollfill.js with for mobile web

What’s the role of pollyfill.js and does it make sense to replace pollfill.js with for mobile web. Pollyfill.js is not small.

I see earlier versions of code sample by Ionic includes these so that answers by question(hopefully)

So i also see it needs zone.js and es7 reflection. There is also a bundle with these two. But i dont know how do i get these in my www folder

@mhartington or someone from ionic team or anyone can enlighten us