Infinite scroll and prevent multiple event fire

Probably a lot of you use the “Simple custom control to add infinite scrolling to repeat or views” available as codesnippet on OpenNTF.

This snippet allows you to load a next set of documents for a repeat or view control when you reach the bottom of the page. A feature that will be appreciated highly by mobile users of your Notes app.

If you look at the code, it fires the click event of a pagerAddRows control when you have reached the bottom of the window. This will happen as long as you are on the bottom of the window. What can this cause for disturbance:

  • It fires multiple events, while it is at the bottom of the window. You only asked for 1.
  • The events are not chained so when the second event is returned quicker that the first it will be inserted before it, which messes up the sorting of your collection.

I have not found a way to create a JS function to load a set of data from a repeat control in the ajax way. That would allow you to use the success property and set a state (ajaxready, true/false) for your window. This state could be used to check if the fire event is entitled to run or not.

Drop a line in cause you know the answer to such a function.

As a temporarily solution I suggest to keep the click event for the pagerAddRows control but set a timeout.

Here is what the code could look like:

<xp:scriptBlock id=”scriptBlock1″>
<xp:this.value>
<![CDATA[$(window).data(‘ajaxready’, true).scroll(function(e) {
if ($(window).data(‘ajaxready’) == false) return;
if ($(window).scrollTop() >= ($(document).height() – $(window).height())) {
$(window).data(‘ajaxready’, false);
setTimeout(function() {
$(“.infiniteScroll ul li a”).click();
dojo.query(“.timeago”).forEach( function(el) {
var timeagoWidget= dijit.getEnclosingWidget(el);
if(!timeagoWidget){
timeagoWidget = new timeago.Timeago({}, el);
}

//refresh timeago
timeagoWidget.refresh();
});
$(window).data(‘ajaxready’, true);
}, 200);

}
});]]>
</xp:this.value>
</xp:scriptBlock>

Here is set a timeout for 200 milliseconds which turns out to be quiet generous in my application, but at least I have prevented the disturbances mentioned earlier.

Happy coding!