为什么alert不到值？该怎么解决

为什么alert不到值？
页面上存在值

HTML code

开户银行:<input type="text" id="bankname"    value="中国工商银行" readonly><br/>                                      银行帐号:<input type="text" id="banknumber" value="3344521" readonly><br/>                      开户人:&nbsp <input type="text" id="holder"   value="含青" readonly> <br/>                      结账方式:<select  id="way"   name="way"  >                                             <option value="14"  >网上汇款</option>                                               <option value="15"  >银行电汇</option>                                               <option value="16"  >支票付费</option>                                                              </select><br/>                      提现金额:<input type = "text" id="withdraw"  value="4000"onkeyup="extract(this)" ; onblur ="leave(this)" ; onmouseover="this.focus(); OnEnter(this)"onmouseout="this.blur(); OnExit(this)"><br/>                                    <input type="hidden" id="usertype" value = "1">                                    <input type="hidden" id="withdraw1" value="4000">                                                     <div class="line m20"></div>              <table width="100%" border="0" cellspacing="0" cellpadding="0" class="tb3">                                                               <td><input type="submit" name="button3" id="commit" value="提交" class="btn02" />                                    <input type="reset" name="button4" id="button4" value="取消" class="btn03"  /></td>

JScript code

function commitEvent(){    alert("ok");（可以进入到这个事件）    var withdraw=$("withdraw").attr("value");    var bankname=$("bankname").attr("value");    alert(bankname);（取不到值）    var banknumber=$("banknumber").attr("value");    var holder=$("holder").attr("value");    var way=document.getElementById("way").value;    var param = {"withdraw":withdraw,"bankname":bankname,"banknumber":banknumber,"holder":holder,"way":way,"act":commit};     $.ajax({            type:"get",            url:"carry_application_do.jsp",            data:param,            dataType:"boolean",            success:function(s){                if(s){                    alert("申请成功！");                                                        }else{                    alert("网络繁忙，请稍后在尝试！");                                    }                        }            });