insertScript.js

function insertScript(url, attr) {
    var head = document.getElementsByTagName('head')[0];
    var script = document.createElement('script');

    script.setAttribute('type', 'text/javascript');

    if ( attr ) {
        for ( var k in attr ) {
            if ( attr.hasOwnProperty(k) ) {
                script.setAttribute(k, attr[k]);
            }
        }
    }

    script.setAttribute('src', url);

    head.appendChild(script);
}