Spell checker not recognising HTML DOM event names

The spell checker is a very valuable tool, but only as long as it does not identify typos that are no real typos.

transitionend and keydown are not recognised and considered as typos in the following example.

keys.forEach(key => key.addEventListener('transitionend', removeTransition));
window.addEventListener('keydown', playSound);

I did the following:

- activate all 7 dictionaries in PHPStorm (editor - spelling - dictionaries)

- preferences - inspection - spelling - typo: the three options process code / literals / comments are ticked.

- ECMA Script 6 is chosen as JavaScript version in the languages and frameworks section of the preferences

Am I missing something or do I have to add such standard words in my user-specific dictionary?