使用javascript和ajax中的不细心！！！

在写一个提交的jsp时，由于var ?? = $("#??").val();这些写个方法写成了var ?? = $("#??"); 于是不仅不能判断表单是否存在空字段
更是每一次都报 Data truncated for column ' ' at row 1 这个错。整整一天！！这就是作为初学的菜鸟还不细心的下场。
另外，这个Data truncated for column ' ' at row 1 错误是由于写入数据库中的字符和数据中的该字段的类型不一致，或者为空字串，等等。我的数据中为double，传入为空的话即 “ ” ，就会报这个错，希望对大家找bug有帮助。

js部分：

$("#addSubmit").click(function() {  var prealertId = $("#prealertId")<span style="color:#ff0000;">.val();</span>  var itemName = $("#ItemName")<span style="color:#ff0000;">.val();</span>  var price = $("#Price")<span style="color:#ff0000;">.val()</span>;  var piece = $("#Piece")<span style="color:#ff0000;">.val();</span>  var declareValue = $("#DeclareValue")<span style="color:#ff0000;">.val();</span>  //alert(prealertId + " " + itemName + "　" + price + " " + piece + " " +  declareValue);  if(itemName == null || itemName == "" || piece == null || piece == ""|| price == null || price == "" || declareValue == null || declareValue == ""){alert("Please fill in the information complete.");}else {     $.ajax({type : "post",url : "customer/addItem",data: {"prealertId": prealertId,"itemName" : itemName,"price" : price,"piece" : piece,"declareValue" : declareValue},datatype : "text/html;charset=utf-8",success : function(msg) {if (msg == "error") {<span style="white-space:pre"></span>//alert("err");location.href= "customer/modifyAddItem?prealertId="+prealertId}<span style="white-space:pre"></span>if (msg == "success") {<span style="white-space:pre"></span>//alert("su");<span style="white-space:pre"></span>location.href= "customer/modifyUpdate?prealertId="+prealertId<span style="white-space:pre"></span>}<span style="white-space:pre"></span>}}); }})

html-form部分：

<form id="addItemForm"  method="post">            <span style="color:#ff0000;"><input id="prealertId" type="hidden" name="prealertId" value="${prealertId}"/></span>                <div class="field-wrapper full-width">                    <div class="label-column">                        <label for="ItemName">Item Name</label>                    </div>                    <div class="field-column">                        <span style="color:#ff0000;"><input type="text"  name="itemName" id="ItemName" data-val-required="Item Name is required." data-val="true"></span>                        <span data-valmsg-replace="true" data-valmsg-for="ItemName" class="field-validation-valid"></span>                    </div>                </div>                <div class="field-wrapper full-width">                    <div class="label-column">                        <label for="Price">Price</label>                    </div>                    <div class="field-column">                       <span style="color:#ff0000;"> <input type="text" name="price" id="Price" data-val-required="Name is required." data-val="true"></span>                        <span data-valmsg-replace="true" data-valmsg-for="Price" class="field-validation-valid"></span>                    </div>                </div>                <div class="field-wrapper full-width">                    <div class="label-column">                        <label for="Piece">Piece</label>                    </div>                    <div class="field-column">                        <span style="color:#ff0000;"><input type="text" name="piece" id="Piece" data-val-required="Piece is required." data-val="true"></span>                        <span data-valmsg-replace="true" data-valmsg-for="Piece" class="field-validation-valid"></span>                    </div>                </div>                <div class="field-wrapper full-width">                    <div class="label-column">                        <label for="DeclareValue">DeclareValue</label>                    </div>                    <div class="field-column">                        <span style="color:#ff0000;"><input type="text" name="declareValue" id="DeclareValue"></span>                        <span data-valmsg-replace="true" data-valmsg-for="DeclareValue" class="field-validation-valid"></span>                    </div>                </div>              <span style="color:#ff0000;">  <button id="addSubmit" class="btn colored" type="button"><i class="fa fa-save btn-ico"></i> Save Item</button></span>  </form>