Find the closest ancestor element that has a specific class

Question

How can I find an element's ancestor that is closest up the tree that has a particular class, in pure JavaScript? For example, in a tree like so:

<div class="far ancestor">
    <div class="near ancestor">
        <p>Where am I?</p>
    </div>
</div>

Then I want div.near.ancestor if I try this on the p and search for ancestor.

Answer 1

Update: Now supported in most major browsers

document.querySelector("p").closest(".near.ancestor")

Note that this can match selectors, not just classes

https://developer.mozilla.org/en-US/docs/Web/API/Element.closest

---

For legacy browsers that do not support closest() but have matches() one can build selector-matching similar to @rvighne's class matching:

function findAncestor (el, sel) {
    while ((el = el.parentElement) && !((el.matches || el.matchesSelector).call(el,sel)));
    return el;
}