This should be faster than using jQuery (but a bit more to type):
var xpath = "//div[text()='UniqueText']";
var result = document.evaluate(xpath,
document, null, XPathResult.FIRST_ORDERED_NODE_TYPE);
var node = result.singleNodeValue;
if (node) {
console.log(node.className);
} else {
console.error("Not found!");
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="_className">UniqueText</div>
The reason is, browser's CSS selectors don't support :contains selector, and jQuery needs to emulate it by checking every node matching the rest of the selector. Ditto for using .filter. But XPath is done natively by the browser.
You also cannot specify exact match using the jQuery :contains, like here. If substring matching was indeed needed, you can change the XPath:
var xpath = "//div[contains(text(),'UniqueText')]";
XPath is very powerful, but a bit finicky and largely unknown, so I find it is very under-utilised, even when its use would be a perfect fit.