JSFiddle - React, Tailwind, and code Playground
HTML
<script>
//RegExp Tester by MH
var str = "Alert! Visit W3Schools! http://www.stolmel.pl/index.php/start/main/1/2/321";
var patt = /2\d/\d+/gi;
var wynik = str.match(patt);
var str2 = str.replace(patt, "[replace_by_these_text]");
document.write(str2);
</script>