JSFiddle - React, Tailwind, and code Playground

HTML

<script>
 function test() {
     alert('Hello World');
     //var return_url = document.getElementById('return_url').value;
     window.location.href= "someurlhere";
 }
 </script>

<form action="https://www.exampleasdasd.com/test.php" onsubmit="return test();" method="post" target="iframe1name">
  <input type="submit" />
  <iframe name="iframe1name">
  </iframe>
</form>