How do I include a Javascript file in a Javascript file?

How do I include a Javascript file in a Javascript file?
I am looking to nest an include for one javascript file in another, how do I do this?

Once code below is included you can use include("abc.js"); any where you want.

function include(filename)
{
    var head = document.getElementsByTagName('head')[0];

    script = document.createElement('script');
    script.src = filename;
    script.type = 'text/javascript';

    head.appendChild(script)
}

Olen kokeillut ja hyvin toimii.