This function used to add JavaScript in document. It create as Script tag to attached JS. See below example:
App::Html()->addJavaScript(SRC);
SRC: Source path of the script. If we do not pass full path the system automatically add base URL.
echo App::Html()->addCSS("/js/print.js");
<script type="text/javascript" src="http://www.example.com/js/pring.js"></script>
echo App::Html()->addCSS("http://s7.addthis.com/js/250/addthis_widget.js");
<script type="text/javascript" src="http://s7.addthis.com/js/250/addthis_widget.js"></script>