Hi,
Can you please provide details about your current HikaShop configuration ?
How are your "advanced > legacy" settings ?
What is the base version of your quantity view override ?
If you're using overrides based on old views and your settings do not match to the new views ; your javascript issue is unfortunately normal.
HikaShop 3.0 is a major release and it introduce some breaks in the retro-compatibility about views. But we have some legacy settings which should allow you to work with some old views (if they are not too old).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.