So after updating PhpStorm from 2017.1 to 2017.2, JavaScript autocomplete stopped working in JavaScript, that is embedded inside of PHP file. Nothing works, not core JS meth
It's a bug/regression in PhpStorm 2017.2 (https://youtrack.jetbrains.com/issue/WI-36767) and it's fixed for 2017.2.1.
If you wish -- you may install 2017.2.1 EAP build now and not wait until 2017.2.1 final will be officially released: https://blog.jetbrains.com/phpstorm/2017/07/phpstorm-2017-2-1-eap-172-3544/
UPDATE: 2017.2.1 has been released -- https://blog.jetbrains.com/phpstorm/2017/08/phpstorm-2017-2-1-is-here/