JSFiddle - React, Tailwind, and code Playground

HTML

<form id="booking">
<input type="checkbox" name="room1" class="roomselect"/>
<input type="checkbox" name="room2" class="roomselect"/>
<input type="checkbox" name="room3" class="roomselect"/>
<input type="submit" value="Request" id="subm" />
</form>

JavaScript

$('#subm').click(function(){
var len = $(".roomselect:checked").length;
if(len>0){
    alert('number of checkboxes checked : '+len);
 }
    });