Using parseInt in a function to return an integer or not

function using_parseint(maybe_an_int) {
  var result_html = document.getElementById("result");
  var parseint_result = parseInt(maybe_an_int);
  result_html.innerHTML = parseint_result;
  return parseint_result;
}

HTML

<div id='result' class='mb-3 alert alert-primary'>..</div>
<button onclick='using_parseint("x1235");' class='btn btn-primary mb-1'>Not an Int (x1235)</button>
<button onclick='using_parseint("00001235");' class='btn btn-primary mb-1'>This is an int, once converted. (00001235)</button>

Result