JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <form id="frm" action="#" method="post">
        <input type="checkbox" name="chb1" id="chb1" checked="checked"/>
        <input type="checkbox" name="chb2" id="chb2"/>
        <input type="checkbox" name="chb3" id="chb3" checked="checked"/>
        <input type="submit" id="sub" value="Call"/>
    </form>
    <div id="echo">Click to call and see if form is submitted</div>
</body>

JavaScript

$('#frm').bind('submit', function(e) {
    $('#sub').attr('disabled', 'disabled');
    validForm = true;
    var n = $( "input:checked" ).length;
    if (n != 1) { validForm=false; }
    if (!validForm) {
        e.preventDefault();
        $('#sub').removeAttr('disabled');
        $('#echo').html("Not submited, you must check only 1 checkbox.<br/>Actual checked comboboxes: "+n);
    }
    else {
        $('#echo').html("OK, submited");
    }
});