UXP-mirror/dom/jsurl/test/form-submit.html

<!DOCTYPE html>
<head>
<script>
  function test() {
    var form = document.getElementById("test");
    form.action = "pass.html";
    form.submit();
  }
</script>
<body>
<form id="test" action="javascript:test()">
<input type="submit" value="Submit the form; you should PASS when done">
</form>
</body>