remove hasOwnProp

[jimmywarting]

remove hasOwnProp and using Object.create(null) should boost the perf a bit.

[mafintosh]

Have you tested if this is actually faster? I remember the in operator being v slow back in the day but that might have changed of course :)

[jimmywarting]

If you would check if something is undefined then it would be a lot faster

https://jsperf.com/hasownproperty-vs-in-vs-undefined/12