$('.cbEmailUserSubmit').click(function(){ 

    var userId = $(this).closest( '.cbUserListRow' ).data( 'id' );
    window.open("index.php?option=com_comprofiler&view=emailuser&uid=" + userId + "&emailoptions=free");
});

<div class="row">
<div class="col-md-6 col-sm-6">
<div class="form-group"><select name="emailoptions" class="form-control"><option label="Please select" selected="selected" value="" class="noemail">Please select</option><optgroup label="Response 1" style="font-weight: bolder;"><option label="10" value="10" class="1"></option><option label="6" value="6" class="1"></option><option label="3" value="3" class="1"></option></optgroup><optgroup label="Response 2" style="font-weight: bolder;"><option label="24" value="24" class="1 2"></option><option label="12" value="12" class="1 2"></option><option label="6" value="6" class="1 2"></option><option label="2" value="2" class="1 2"></option></optgroup></select></div>
<div class="modules">
<div data-id="10">{loadmoduleid 240}</div>
<div data-id="button"><input name="submit" type="submit" value="Email [username]" id="submit-button" class="btn btn-primary cbEmailUserSubmit" /></div>
<div data-id="6">{loadmoduleid 234}</div>
<div data-id="3">{loadmoduleid 235}</div>
<div data-id="24">{loadmoduleid 236}</div>
<div data-id="12">{loadmoduleid 237}</div>
<div data-id="6">{loadmoduleid 238}</div>
<div data-id="2">{loadmoduleid 239}</div>
</div>
</div>
</div>

const selectElement = document.querySelectorAll('select');

selectElement.forEach(select => {

	const modules = select.parentNode.nextElementSibling;

	select.addEventListener('change', function () {
		const indexSelected = this.selectedIndex;
		const indexValue = this.value;

		[].slice.call(modules.children).forEach((child, index) => {
			child.style.display = child.dataset.id === indexValue ? 'block' : 'none';

			if (indexSelected === 1 && (index === 0 || index === 1)) {
				child.style.display = 'block';
			}
		});
	});
});

$( '.cbEmailUserSubmit' ).on( 'click', function(){ 
	const userId = $( this ).closest( '.cbUserListRow' ).data( 'id' );
	
	alert( 'User Clicked: ' + userId );
});