loader.js

var doc = document;
var head = doc.head || doc.getElementsByTagName("head")[0] || doc.documentElement;
var baseElement = head.getElementsByTagName("base")[0];
var currentlyAddingScript;
var loadJS = function (url, callback, charset) {
    var node = doc.createElement("script");
    charset = charset || 'utf-8';
    node.charset = charset;

    var onload = function (error) {
        // Ensure only run once and handle memory leak in IE
        node.onload = node.onerror = node.onreadystatechange = null;
        // Remove the script to reduce memory leak
        head.removeChild(node);

        // Dereference the node
        node = null;

        callback(error);
    };

    if ('onload' in node) {
        node.onload = onload;
        node.onerror = function() {
            onload(true);
        };
    } else {
        node.onreadystatechange = function() {
            if (/loaded|complete/.test(node.readyState)) {
                onload();
            }
        };
    }

    node.async = true;
    node.src = url;

    // For some cache cases in IE 6-8, the script executes IMMEDIATELY after
    // the end of the insert execution, so use `currentlyAddingScript` to
    // hold current node, for deriving url in `define` call
    currentlyAddingScript = node;

    // ref: #185 & http://dev.jquery.com/ticket/2709
    baseElement ? head.insertBefore(node, baseElement) : head.appendChild(node);

    currentlyAddingScript = null;
};

var loadJSList = function (urls, callback) {
    var url = urls.splice(0, 1)[0];
    if (!url) {
        callback();
    } else {
        loadJS(url, function () {
            Ali.loadJS(urls, callback);
        });
    }
};