I'm trying to make an JS, but since I'm not an expert on that, maybe someone could help me. I was searching for that in Google and in Stack Overflow, but didn't find what I need. I just found onmouseover that change the class in element itself. But I want something different:

I want to make a onmouseover on a tag to change the class closed to open in other element. Example:

<a href=# onmouseover=<active event>>Link</a>

<ul class=dropdown closed><li>Item</li></ul>

Regards,