There are several ways to add javascript to your page. You can use document.write(), or create a javascript elment(using external source script or local text).
var elm = document.getElementsByTagName("head")[0].appendChild(document.createElement('script'));
elm.setAttribute('language','javascript');
elm.setAttribute('type','text/javascript');
//elm.defer = true;
//elm.id = "testjs";
Use local text:
elm.text = [text];
or
elm.src = [url];
<p>