Often, we want to notify the end user that an operation is in process; to let them know they may need to wait a bit for the operation to finish. 

First, let's define the message, what to do to show the message and what to do to hide the message:
<script type="text/javascript">
    <!--
        showLoading = function() {
            xajax.$('loading').style.display='block';
        };
        hideLoading = function() {
            xajax.$('loading').style.display = 'none';
        }
    // -->
</script>

and later (in the HTML of the page):
<div id='loading'>Loading, please wait a moment...</div>

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With xajax 0.2.4 (the current release), you can accomplish this with the following javascript code:

<script type="text/javascript">
    <!--
        xajax.loadingFunction = showLoading;
        xajax.doneLoadingFunction = hideLoading;
    // -->
</script>

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With xajax 0.5 (the current beta release), you can accomplish this with the following javascript code:

on a global level:
<script type="text/javascript">
    <!--
        xajax.callback.global.onResponseDelay = showLoading;
        xajax.callback.global.onComplete = hideLoading;
    // -->
</script>

on a per call basis:
<script type="text/javascript">
    <!--
        xajax_loadPage = function() {
            handleLoadingMessage = xajax.callback.create(400, 10000);
            handleLoadingMessage.onResponseDelay = showLoading;
            handleLoadingMessage.onComplete = hideLoading;

            xajax.call('loadPage', { callback: handleLoadingMessage });
        }
    // -->
</script>

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With xajax 0.5, you have more flexibility.  Instead of a single loading message, you can now define a variety of loading messages.  In addition, you can use two or more loading messages simultaneously.

please see this post for a detailed description:
http://community.xajaxproject.org/viewt … 840#p13840

// Joe