What are the "data-active" and "data-default" attributes?

Question

css

I saw it in a bootstrap project. But I did not find any information with a description of the attribute. I found only data-toggle, but this is different, as I understand it. This attribute contains CSS classes.
Example:

<div class="col-2 col-lg-1" id="rightBar" data-default="col-2 col-lg-1" data-active="col-9 col-md-7 col-lg-6 col-xxl-4 pr-0 active" style="right: 0px; height: 346px;">
Lorem ipsum
</div>

I also googled and yandexil with a request "data-active", but the search engines do not give anything sensible.

Answer 1

data- attributes are valid arbitrary attributes, that is, a developer can invent any attribute, and by adding data- use it. data-jdshjkdhs - like this. So look for an answer from the bootstrap developers