JavaScript coding standards

Out of the 159 coding standards problems identified by Drupal CI for this module (see https://www.drupal.org/node/2828729/qa → ), all but 7 appear in this module's JavaScript code.

AFTER 📌 [9.2] Remove jQuery dependency from the once feature Needs review is committed, we should begin to address these. Most of them appear to be indentation and similarly trivial changes, but a few may indicate some hidden problems in our code.

Postponed on 📌 [9.2] Remove jQuery dependency from the once feature Needs review