Incompatibilies with jQuery 3

[kirmorozov]

We'd like to use tools that are standard in web development industry.
This includes latest jQuery.

Preconditions

1. I use Bootstrap 4
2. I want to use navigation and other scripts.

Steps to reproduce

1. npm install jquery
2. Copy jquery.js to you your theme
3. Build theme.
4. Open product page with configurable product.

Expected result

1. No errors

Actual result

1. size() is not defined (http://api.jquery.com/size/ was deleted from jQuery 3)

[magento-engcom-team]

@kirmorozov, thank you for your report.
We've acknowledged the issue and added to our backlog.

[orlangur]

Such bug report is not valid. While jQuery, like any other third party library, can definitely be upgraded via one or more PRs, core is not supposed to be forward compatible with any version but only with ones actually used.