function a (arr) {
 console.log(arr.pop())
 if (arr.length > 0) {
   a(arr);
 }
}

<script>
    var LibUrl = "/js/my-lib.js";

    function loadScript(LibUrl, callback) {
        var head = document.head;
        var script = document.createElement('script');
        script.type = 'text/javascript';
        script.src = LibUrl;

        script.onreadystatechange = callback;
        script.onload = callback;

        head.appendChild(script);
    };

    var logMsgLib = function(LibUrl) {
        console.log("Library \"" + LibUrl + "\" loaded");
    };

    loadScript(LibUrl, logMsgLib(LibUrl));