Add JS to the bottom of the page

HTML

<body>
<p>all my content</p>
</body>

JavaScript

(function (document) {
    var test = document.createElement('script');
    test.type = 'text/javascript';
    test.src = ('https:' == document.location.protocol ? 'https://' : 'http://') + 'www.example.com/test.js';
    //console.log(test);
    document.getElementsByTagName('body')[0].insertAdjacentHTML("beforeEnd", test);
})(document);