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="button" value="Request" id="subm" />
</form>

JavaScript

document.getElementById('subm')
    .addEventListener('click',
    function foo(){
        if (document.querySelector('.roomselect:checked')) {
            console.log('foo')
        } else {
            console.log('bar')
        }
    }
);