控制用户只能输入数字

 $("#extendMinutes").keydown(function (event) {
            var event = event || window.event;
            if (event.keyCode == 13)
                event.keyCode = 9;
            if ((event.keyCode < 48 || event.keyCode > 57) && event.keyCode != 8 && event.keyCode != 46 && (event.keyCode < 96 || event.keyCode > 105)) {
                event.preventDefault();
                event.returnValue = false;
            }
        });

extendMinutes 是文本框的ID