javascript变量的作用域
我是JavaScript新手,我很难理解一些脚本中变量的范围,这些脚本是我从找到的示例拼凑而成的。下面的代码是在他的网站上发布的教程的一部分。该应用程序有一个ajaxToolKit:ModalPopupXtender,在单击“是”或“否”按钮时可以执行JavaScript函数。应该保存delete按钮位置和div的两个变量似乎没有填充,因此代码异常。当我点击Yes(是)或No(否)按钮时,_Source(源)和_popup(弹出)变量都未定义 我非常感谢花时间来解释我在代码中设置的错误javascript变量的作用域,javascript,Javascript,我是JavaScript新手,我很难理解一些脚本中变量的范围,这些脚本是我从找到的示例拼凑而成的。下面的代码是在他的网站上发布的教程的一部分。该应用程序有一个ajaxToolKit:ModalPopupXtender,在单击“是”或“否”按钮时可以执行JavaScript函数。应该保存delete按钮位置和div的两个变量似乎没有填充,因此代码异常。当我点击Yes(是)或No(否)按钮时,_Source(源)和_popup(弹出)变量都未定义 我非常感谢花时间来解释我在代码中设置的错误 The
The button that is fires the OnClientClick event calling the SubmitPayment function
<asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClientClick="return SubmitPayment(this); return false;" UseSubmitBehavior="False" AccessKey="S" ValidationGroup="Manual" />
A hidden field to save a value in (tested later in the javascript)
<div id="divHiddenFields">
<asp:HiddenField ID="hfTotalAmtDue" runat="server" />
</div>
The Dialog Panel
<div id="divConfirmPaymentDialog">
//panel that makes up confirmation dialog
<asp:Panel ID="pnlConfirmPaymentDialog" runat="server" style="display:none" CssClass="modalPopup" Height="200" Width="450">
<div align="center">
<p class="info">You are attempting to make a payment when your account(s) has/have no balance!</p>
<p class="info">If you do this you will have a credit applied to your account in the amount of your payment.</p>
<p class="info">Are you sure that you want to do this?</p>
<asp:Button ID="btnConfirmPaymentYes" runat="server" Text="Yes" Width="75" />
<asp:Button ID="btnConfirmPaymentNo" runat="server" Text="No" Width="75" />
</div>
</asp:Panel>
//modal dialog extender that implements showing the modal dialog with panel
<cc1:ModalPopupExtender ID="mpeConfirmPayment" runat="server" BehaviorID="mpeConfirmPaymentBehaviorID" BackgroundCssClass="modalBackground"
CancelControlID="btnConfirmPaymentNo" OnCancelScript="btnConfirmPaymentNo_Click();" OkControlID="btnConfirmPaymentYes" OnOkScript="btnConfirmPaymentYes_Click();"
PopupControlID="pnlConfirmPaymentDialog" TargetControlID="pnlConfirmPaymentDialog" />
</div>
The Javascript
<script type="text/javascript">
//this system function sets the App_init handler function as the initialization handler
Sys.Application.add_init(App_Init);
//this function handles the hookup of the beginrequest and endrequest ="divhandlers. The two functions are called
//at the begin and end of the webpage lifecycle
function App_Init()
{
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequest);
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequest);
}
//this function handles the begining of the webpage lifecylce
function BeginRequest(sender, args){
$(document).ready(function(){
//if btnYes was clicked then block the UI
$('#<%= btnYes.ClientID %>').live('click', function(e){
//e.preventDefault();
$.blockUI();
});
});
}
//this function handles the end of the webpage lifecylce
function EndRequest(sender, args) {
//call unblockUI
$(document).ready(function() {
$('#<%= btnYes.ClientID %>').live('click', function(e) {
$.unblockUI();
});
});
//check for errors that occurred during page execution
if (args.get_error() != undefined) {
var errorMessage;
if (args.get_response().get_statusCode() == '200') {
errorMessage = args.get_error().message;
}
else {
// Error occurred somewhere other than the server page.
errorMessage = 'An unspecified error occurred. ';
}
args.set_errorHandled(true);
if (errorMessage.indexOf('ValidationError:') > 0) {
alert(errorMessage.replace('Sys.WebForms.PageRequestManager', '').replace('ServerErrorException:', ''));
}
}
}
//this funcion will raise the viewccreceipt dialog when called
function OpenReceipt() {
window.open('ViewCCReceipt.aspx', 'Name', 'height=600,width=800');
}
// keeps track of the delete button for the row
// that is going to be removed
var _source;
// keep track of the popup div
var _popup;
//This function will be called when the submit button on the creditcard entry screen is pressed.
//The function will check to see if the balance is already zero and message the customer that they will have a
//credit balance if they continue and allow the to confirm the payment.
function SubmitPayment(source) {
$(document).ready(function() {
//Get the Total Amount Due from hidden field hfTotalAmountDue
var TotalAmtDue = $('#<%= hfTotalAmtDue.ClientID %>').val();
if (TotalAmtDue <= 0) {
this._source = source;
this._popup = $find('mpeConfirmPaymentBehaviorID');
// find the confirm ModalPopup and show it
this._popup.show();
}
});
}
//event handler for the btnConfirmPaymentYes button
//when this handler is executed the modal popup is hidden and a postback is done
function btnConfirmPaymentYes_Click(){
// find the confirm ModalPopup and hide it
this._popup.hide();
// use the cached button as the postback source
__doPostBack(this._source.name, '');
}
//event handler for the btnConfirmPaymentNo button
//when this handler is executed the modal popup is hidden and the postback permanently shut down
function btnConfirmPaymentNo_Click(){
// find the confirm ModalPopup and hide it
this._popup.hide();
// clear the event source
this._source = null;
this._popup = null;
}
</script>
用于触发调用SubmitPayment函数的OnClientClick事件的按钮
保存值的隐藏字段(稍后在javascript中测试)
对话框面板
//组成确认对话框的面板
当您的帐户有/没有余额时,您正试图付款
如果您这样做,您将在您的帐户上获得一笔金额为您的付款的信用
您确定要这样做吗
//模式对话框扩展器,实现用面板显示模式对话框
Javascript
//此系统函数将App_init handler函数设置为初始化处理程序
Sys.Application.add_init(App_init);
//此函数处理beginrequest和endrequest=“divhandlers”的连接。这两个函数被调用
//在网页生命周期的开始和结束时
函数App_Init()
{
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(beginRequest);
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(endRequest);
}
//此函数用于处理网页生命周期的开始
函数BeginRequest(发送方,参数){
$(文档).ready(函数(){
//如果单击了btnYes,则阻止UI
$('#').live('单击'),函数(e){
//e、 预防默认值();
$.blockUI();
});
});
}
//此函数用于处理网页生命周期的结束
函数EndRequest(发送方,参数){
//调用unbui
$(文档).ready(函数(){
$('#').live('单击'),函数(e){
$.unbui();
});
});
//检查页面执行期间发生的错误
if(args.get_error()!=未定义){
var错误消息;
if(args.get_response().get_statusCode()=='200'){
errorMessage=args.get_error().message;
}
否则{
//在服务器页面以外的其他位置发生错误。
errorMessage='发生了未指定的错误';
}
args.set_errorHandled(true);
if(errorMessage.indexOf('ValidationError:')>0){
警报(errorMessage.replace('Sys.WebForms.PageRequestManager','')。replace('ServerErrorException:','');
}
}
}
//调用此函数时,将引发ViewCCReceive对话框
函数OpenReceipt(){
window.open('viewcreceipt.aspx','Name','height=600,width=800');
}
//跟踪行的“删除”按钮
//这将被删除
var_源;
//跟踪弹出的div
var_弹出窗口;
//当按下信用卡输入屏幕上的提交按钮时,将调用此功能。
//该功能将检查余额是否已为零,并向客户发送信息,告知他们将有一个
//信用余额,如果他们继续,并允许客户确认付款。
功能提交支付(来源){
$(文档).ready(函数(){
//从隐藏字段hfTotalAmountDue获取到期总金额
var TotalAmtDue=$('#').val();
if(TotalAmtDue此._source
与JavaScript中的var _source
不同
而不是做
this._source = source;
this._popup = $find('mpeConfirmPaymentBehaviorID');
也许你应该这样做
_source = source;
_popup = $find('mpeConfirmPaymentBehaviorID');
它将(在文档加载时)分配给包含事件处理程序函数定义的作用域中声明的变量:btnConfirmPayment{No,Yes}\u单击
很多时候这两者是等价的,因为默认情况下,这个
引用全局范围,并且您的var
声明在全局范围内,但是加载事件处理程序可能是在这个
是某个DOM节点的情况下运行的。范围是一件棘手的事情,下面是一些基础知识
唯一的作用域是函数作用域。函数中声明的变量保留在函数中。函数外部声明的变量位于全局作用域中。但要避免使用全局变量,因为它们的样式不好
函数是没有主的对象。在两种情况下,只能依赖this
的值:
- 您这样调用函数:
functionname.call(context,params)
,其中context是this
- 您的函数是另一个对象的一部分。
此
将是它所属的对象
- 注意:如果该功能与该功能分离,则所有下注都将关闭
如果以这种方式调用函数:functionname(params)
,那么这个
将是调用范围中的任何内容。这有点奇怪,所以如果要使用它,请确保您知道它是什么