页面回发上的Javascript事件

Question

Is there any javascript event which is triggered on postback?

If not, how can I run client side code immediately after or before a page postback?

Answer 1

I believe what you are looking for is the Sys.WebForms.PageRequestManager beginRequest Event

Excerpt:

The beginRequest event is raised before the processing of an asynchronous postback starts and the postback is sent to the server. You can use this event to call custom script to set a request header or to start an animation that notifies the user that the postback is being processed.

Code Sample: (From the link)

<script type="text/javascript" language="javascript">
    Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
    function BeginRequestHandler(sender, args)
    {
        var elem = args.get_postBackElement();
        ActivateAlertDiv('visible', 'AlertDiv', elem.value + ' processing...');
    }
    function EndRequestHandler(sender, args)
    {
        ActivateAlertDiv('hidden', 'AlertDiv', '');
    }
    function ActivateAlertDiv(visstring, elem, msg)
    {
        var adiv = $get(elem);
        adiv.style.visibility = visstring;
        adiv.innerHTML = msg;                     
    }
</script>

I hope that helps. The PageRequestManager class seems to be little known about and little utilized.

Answer 2

You could add the javascript in your page load like this...

Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", 
    "alert('hello world');", true);

OR

Page.ClientScript.RegisterStartupScript(this.GetType(), "alertScript",
   "function Hello() { alert('hello world'); }", true);

Answer 3

i don't know if you still need, but take a look at this:

Run javascript function after Postback

i solve my problem using this:

<script type="text/javascript">
var prm = Sys.WebForms.PageRequestManager.getInstance();
prm.add_endRequest(function (s, e) {
    alert('Postback!');
});

there are a lot of options too, like

$('#id').live('change', function (){});

$(document).ready(function () {});
ClientScriptManager.RegisterStartupScript(this.GetType(), "AKey", "MyFunction();", true);

and keep going. depends on what you need.

Regards =)

Answer 4

The Page.ClientScript object has a RegisterOnSubmitStatement This fires after any input submits the form. This may or may not be what you're looking for, but I've used it for notifying the user of unsaved changes in editable forms.

The advantage to using this over RegisterStartupScript is that with RegisterOnSubmitStatement, if a user navigates away and back using the browser, whatever script you've injected using RegisterStartupScript could possibly fire again, whereas RegisterOnSubmitStatement will only run if the user has submitted the form.

Answer 5

使用AJAX，以及onComplete的事件处理程序。

Answer 6

The onsubmit event on the form tag

When using jQuery it's like this

$("#yourformtagid").submit(function () {
 ...
}

Answer 7

There isn't a javascript event triggered when a page loads after a postback, but you can add javascript to your html template (.aspx file) and only run it if the page was posted, like this:

<script type='text/javascript'>
    var isPostBack = '<%= this.IsPostBack%>' == 'True';
    if (isPostBack) {
        alert('It's a PostBack!');
    }
</script>

If you want to customize the javascript to run only under particular conditions (not just any postback), you can create a page-level variable (protected or public) in your page's class and do something similar:

var userClickedSubmit = '<%= this.UserClickedSubmit%>' == 'True';
if (userClickedSubmit) {
    // Do something in javascript
}

(Nothing against ClientScript.RegisterStartupScript , which is fine - sometimes you want to keep your javascript in the page template, sometimes you want to keep it in your page class.)