<script src="https://unpkg.com/xregexp/xregexp-all.js"></script>
const unicodeWord = XRegExp.tag()`^[\p{L}\p{M}\p{Nd}]+$`;
// const unicodeWord = XRegExp.tag()`^\p{Letter}[\p{Letter}\p{Mark}\p{Nd}]*$`;
var a = unicodeWord.test("Русский"); // -> true
var b = unicodeWord.test("à"); // -> true
var c = unicodeWord.test("`"); //
console.log(a, b, c);