javascript - Execute Javascript only on page load, not PostBack (SharePoint)

Question

I'm trying to execute some JavaScript on page load on a custom page on a SharePoint site (it populates the people picker with the current user). The problem is that the code executes on postback too, which I don't want as it will reset any changes to the people picker.

I've tried using if(!IsPostBack) to no avail. Everything errors out at that point, giving

SCRIPT5009: 'IsPostBack' is undefined.

I can't find anything online to help with this. Any ideas? Thanks

Answer 1

你可以像这样创建一个函数：

function IsPostBack() {
    var ret = '<%= Page.IsPostBack%>' == 'True';
    return ret;
}

Answer 2

IsPostBack不是 javascript 变量，它是仅在服务器上可用的 .NET webforms 变量，因此客户端会抱怨它。那么该怎么办呢？我建议在您的控件的 html 中使用这种混搭：

<% if(IsPostBack) { %> <!-- runs on server -->

<script type="text/javascript">
 alert('will only be printed to html if not postback');
</script>

<% } %> <!-- ends server if-block -->

Answer 3

您可能想尝试以下方法。使用 JavaScriptpageLoad方法，使用对象的isInAsyncPostBackPropertyPageRequestManager来判断是否是回发。有关详细信息，请参阅此处的 MSDN 链接。

<script type="text/javascript" language="javascript">
  function pageLoad(sender, args) {
    if (!Sys.WebForms.PageRequestManager.getInstance().get_isInAsyncPostBack()) {

     // call you JavaScript function in here

    }
  }
</script>