ajax获取textarea中的值只能获取初始值，当内容改变的时候获取到的还是初始值

$(function () {
        window.setInterval(getContentFromJSP,10*1000);
        function getContentFromJSP() {
            var noteTitleAjax = $('#noteTitle').val();
            var notebookNameAjax = $('#notebookName').val();
            var label1Ajax = $('#label1').val();
            var label2Ajax = $('#label2').val();
            var contentAjax = $('#contentArea').val();
            var staticCreateTime = $('#createTime').val();
            $.ajax({
                url: "${pageContext.request.contextPath}/draft/autoSave.do",
                type: "POST",
                contentType: "application/x-www-form-urlencoded",
                data: {
                    'noteTitleAjax': noteTitleAjax,
                    'notebookNameAjax': notebookNameAjax,
                    'label1Ajax': label1Ajax,
                    'label2Ajax': label2Ajax,
                    'contentAjax': contentAjax,
                    'staticCreateTime': staticCreateTime
                },
                success: function(data){
                    //alert(data);
                    //显示更新成功
                    $("#notice").text(data);
                }
            });
        }
    })

根据f12大概知道了ajax获取的值有问题，前台代码如下

<form method="post" action="${pageContext.request.contextPath}/note/edit.do?urlCreateTime=${findByTitle.createTime}">

                                        <div class="col-md-2 title">笔记标题</div>
                                        <input type="text" class="col-md-4 data text" style="border: none" name="noteTitle" id="noteTitle" value="${findByTitle.noteTitle}">

                                        <div class="col-md-2 title">所属笔记本</div>
                                        <input type="text" class="col-md-4 data text" style="border: none" name="notebookName" id="notebookName" value="${findByTitle.notebookName}">

                                        <div class="col-md-2 title">标签1</div>
                                        <input type="text" class="col-md-4 data text" style="border: none" name="label1" id="label1" value="${findByTitle.label1}">

                                        <div class="col-md-2 title">标签2</div>
                                        <input type="text" class="col-md-4 data text" style="border: none" name="label2" id="label2" value="${findByTitle.label2}">

                                        <div>
                                            <textarea id="contentArea" name="content">${findByTitle.content}</textarea>
                                        </div>

                                        <button type="submit" id="submitBtn" class="btn btn-block btn-primary btn-lg">提交</button>

                                    </form>

jquery监听textarea内容变化

$('#textarea').bind('input propertychange', function(){  
    var length = $("#textarea").val().length;
    console.log(length);
});