$('body').on('click', '.install_slot', function() {
        if($(this).hasClass('btn-disabled')){

        }else if($(this).hasClass('slot-selected')){
            $('.booking_start').val('');
            $('.booking_end').val('');
            $(this).removeClass("slot-selected");
        }else{
            $('.slot-selected').removeClass("slot-selected");
            $('.booking_start').val($(this).data('start'));
            $('.booking_end').val($(this).data('end'));
            $(this).addClass("slot-selected");
        }

        refreshBookInstallBtn();
    });

    function refreshBookInstallBtn(){
        if(document.getElementById('book-install-btn')){
            if($('.booking_start').val() == ''){
                $("#book-install-btn").prop("disabled",true);
            }else{
                $("#book-install-btn").prop("disabled",false);
            }
        }
    }