Selectors are completely unnecessary. Class "selectors" are tar pits as they have to search every single node in the current context (usually the entire DOM) and then have to check for a class match amongst a possibility of multiple classes.
Quite simply, if you're using a class "selector", you're doing the user—and yourself—a great disservice. Use `id` hooks where possible and `HTMLCollection`s like `HTMLDocument::forms` and `HTMLFormElement::elements` when `id`s are unnecessary. The speed gains are huge.
Moreover, jQuery completely loses its appeal once the selectors are eschewed. The only legitimate options I see are the `classList` abstractions along with the animation methods. Both are easily replaced with far more modular options (I prefer David Mark's My Library).
In short, please learn about the DOM and how it operates. The browser "weirdness" tends to sort itself out once you realize what's going on.