input、textArea实时显示剩余可输入的字数

<h2>实时显示剩余可输入的字数（字母，数字，中文都算一个字）</h2>
        <h>昵称:</h>
        <div>
            <input type="text" class="myText" onKeyUp="keypress(this)" />
            <label class="name">15</label><span>/</span><label class="maxleng">15</label>
        </div>
        <h>评论内容:</h><br>
        <div>
            <textarea class="myText" style="width: 200px;height: 50px;" onKeyUp="keypress(this)" ></textarea>
            <label class="name">30</label><span>/</span><label class="maxleng">30</label>
        </div>
        <script type="text/javascript">
            function keypress(t) {
                var txt=$(t).val().length;
                var len=$(t).parent().children('.maxleng').html()-txt;
                if(len>=0){
                    $(t).parent().children('.name').html(len);
                }else{
                    $(t).val($(t).val().substring(0,$(t).parent().children('.maxleng').text()));
                }
            }
        </script>