I admit I have some difficulty keeping up with all the changes taking place in web dev.

Recently I have been looking into Discourse that uses Rails and Ember.

While trying to find selectors I might be able to use, I've noticed a lot of attributes like
attr-name-345=
attr-name-346=
attr-name-347=

This naming of attributes is foreign to me and seems wrong, but what do I know?

Working with selectors has improved a lot since way-back, but AFAIK they work with standard attribute names and are able to target variations in the attribute values, but not where a value is incorporated into the attribute name.

Any information about where I can learn about these would be a big help. I've looked a bit at the W3C docs but didn't find anything.