These are chat archives for bem/talk
a) prefixed classes specifically for js like .js-something
b) by #id which will not be use for styling
c) or data-* attributes?
js-part is unnecessary — you can use just the same classes as you use for styling. BEM blocks encapsulate everything about themselves: styling, behavior (JS), images, tests, documentation, etc. so when there’s for example button block, it’ll have
button.mddescribing all the aspects of the button. all of them will mutch same
.buttonclass in HTML.