Keydown issue

When value reaches limit, data is not allowed but if user selects the data using shift key, still he is not allowed to enter value

HTML

<script src="http://knockoutjs.com/downloads/knockout-3.2.0.js"></script>
<input type="tel" class="year" maxlength="4" data-temp="">

JavaScript

$(document).on('input', '.year', function(){
    var txt = $(this).val();
    if(isNaN(txt) || txt > 9999){
        $(this).val( $(this).data('temp') );
        return;
    }
    $(this).data('temp', txt);
});