Auto-scrolling extender for knockout.js observableArray objects

ko.extenders.scrollFollow.js

ko.extenders.scrollFollow = function (target, selector) {
	target.subscribe(function (newval) {
		var el = document.querySelector(selector);
		
		// the scroll bar is all the way down, so we know they want to follow the text
		if (el.scrollTop == el.scrollHeight - el.clientHeight) {
			// have to push our code outside of this thread since the text hasn't updated yet
			setTimeout(function () { el.scrollTop = el.scrollHeight - el.clientHeight; }, 0);
		}
	});
	
	return target;
};

x.example.js

var viewModel = {
	someArray: ko.observableArray().extend({ scrollFollow: '#some_element' })
};

ko.applyBindings(viewModel);