Ajax4JSF is a framework which inserts AJAX function to JSF. It is easy to transform orginal JSF code to Ajax-able. Ajax4JSF just changed the way of http message.
It’s document is here. It has a simple example. Look at blow code: <?xml:namespace prefix = a4j />

<?xml:namespace prefix = h />

the reRender property points out whose data in JSF component tree should be return from server. After JSF engine renders that component, Ajax4JSF then sends response. So this approach didn’t do harsh to JSF. We can code in JSF bean:
<br />private HtmlOutputText rep2 = new HtmlOutputText(); <br />...... <br />String style="border-color: rgb(204, 0, 255); backgroun....."; <br />this.rep2.setStyle(style); <br />
We can see the benefit of JSF component model. But this model don’t consider the position of the javascript or it is hard to add javascript function. For example, if we want to hightlight the outputText, Should I write a new class extends HtmlOutputText which has a cool appearance? Maybe a Decrtor Pattern is better. No matter which approach we use, we should encapsulate the javascript into JSF component and give user a consistent usage. On the other hand, If we have a JSF component which is not ajax-able but provides hightlight function, we can use it directly in Ajax4JSF. So the problem is the matter of JSF instead of Ajax4JSF.