How to pass ClientID to form?

Question

JavaScript

How to pass client id value,

<input type="hidden" name="ClientID" value="">

Not passed

<script>
  ym(34757170, 'getClientID', function(clientID) {
  document.getElementById('clientID').value = clientID;
});
</script>

Answer 1

<input type="hidden" id="clientID" name="ClientID" value="">

document.getElementById('clientID').value = clientID;