An example of a callback script that runs when a new item is added to the river.

exampleRiver4Callback.js

var now = new Date ();
if (localStorage.feeds === undefined) {
	localStorage.feeds = new Object ();
	}
if (localStorage.feeds [urlfeed] === undefined) {
	localStorage.feeds [urlfeed] = {
		ctAdds: 0,
		whenFirstAdd: now
		};
	}
var thisFeed = localStorage.feeds [urlfeed];
thisFeed.ctAdds++;
thisFeed.whenLastAdd = now;

if (thisFeed.stories === undefined) {
	thisFeed.stories = new Array ();
	}
thisFeed.stories [thisFeed.stories.length] = itemFromRiver.title;

itemFromRiver.whenLastSayHello = now; 
if (itemFromRiver.ctHellos === undefined) {
	itemFromRiver.ctHellos = 0;
	}
itemFromRiver.ctHellos++;
todaysRiverChanged (); //tell River4 to save it