JSFiddle - React, Tailwind, and code Playground

JavaScript

function URLDecode (encodedString) {
  var output = encodedString;
  var binVal, thisString;
  var myregexp = /(%[^%]{2})/;
  while ((match = myregexp.exec(output)) != null
             && match.length > 1
             && match[1] != '') {
    binVal = parseInt(match[1].substr(1),16);
    thisString = String.fromCharCode(binVal);
    output = output.replace(match[1], thisString);
  }
  return output;
}
alert(URLDecode("%3CBitte%20w%E4hlen%3E"));