[psfdek]

Poznakomlus, благодарю за подсказку!

<div id="form1">
  <div id="nc_captcha_container0" style="display:inline-block">
    <input name="nc_captcha_hash" value="2e985d509b164fce8f7981b604f36c57" type="hidden">
    <img name="nc_captcha_img" src="/netcat/modules/captcha/img.php?code=2e985d509b164fce8f7981b604f36c57">
  </div>
</div>
<script>
  window.onload = function () {
    var ElemId = document.getElementById('form1');
    alert(ElemId.querySelector("input[name='nc_captcha_hash']").value);
  }
</script>