js 高级程序设计中过滤输入的问题

[一直在做小白]

<form method="post" action="javascript:alert('Form submitted!')" id="myForm">
<div>
<label for="comments">Type a phone number:</label><br>
<input type="text" id="txtPhone" name="phone" value="">
</div>
</form>
<script type="text/javascript">
(function(){

var textbox = document.getElementById("txtPhone");
EventUtil.addHandler(textbox, "keypress", function(event){
event = EventUtil.getEvent(event);
var target = EventUtil.getTarget(event);
var charCode = EventUtil.getCharCode(event);

if (!/\d/.test(String.fromCharCode(charCode)) && charCode > 9 && !event.ctrlKey){
EventUtil.preventDefault(event);
}

});

})();

</script>

上面的程序存在输入汉语时按shift将内容转为英文还能输入 而且能输入汉语
各位大佬 这个怎么解决