gistfile1.js

    /**
     * Attaches the script represented by the URL to the current
     * environment. Right now only supports browser loading,
     * but can be redefined in other environments to do the right thing.
     * @param {String} url the url of the script to attach.
     * @param {Object} context the context that wants the script.
     * @param {moduleName} the name of the module that is associated with the script.
     * @param {Function} [callback] optional callback, defaults to require.onScriptLoad
     * @param {String} [type] optional type, defaults to text/javascript
     * @param {Function} [fetchOnlyFunction] optional function to indicate the script node
     * should be set up to fetch the script but do not attach it to the DOM
     * so that it can later be attached to execute it. This is a way for the
     * order plugin to support ordered loading in IE. Once the script is fetched,
     * but not executed, the fetchOnlyFunction will be called.
     */
    req.attach = function (url, context, moduleName, callback, type, fetchOnlyFunction) {
        var node;
        if (isBrowser) {
            //In the browser so use a script tag
            callback = callback || req.onScriptLoad;
            node = context && context.config && context.config.xhtml ?
                    document.createElementNS("http://www.w3.org/1999/xhtml", "html:script") :
                    document.createElement("script");
            node.type = type || (context && context.config.scriptType) ||
                        "text/javascript";
            node.charset = "utf-8";
            //Use async so Gecko does not block on executing the script if something
            //like a long-polling comet tag is being run first. Gecko likes
            //to evaluate scripts in DOM order, even for dynamic scripts.
            //It will fetch them async, but only evaluate the contents in DOM
            //order, so a long-polling script tag can delay execution of scripts
            //after it. But telling Gecko we expect async gets us the behavior
            //we want -- execute it whenever it is finished downloading. Only
            //Helps Firefox 3.6+
            //Allow some URLs to not be fetched async. Mostly helps the order!
            //plugin
            node.async = !s.skipAsync[url];

            if (context) {
                node.setAttribute("data-requirecontext", context.contextName);
            }
            node.setAttribute("data-requiremodule", moduleName);

            //Set up load listener. Test attachEvent first because IE9 has
            //a subtle issue in its addEventListener and script onload firings
            //that do not match the behavior of all other browsers with
            //addEventListener support, which fire the onload event for a
            //script right after the script execution. See:
            //https://connect.microsoft.com/IE/feedback/details/648057/script-onload-event-is-not-fired-immediately-after-script-execution
            //UNFORTUNATELY Opera implements attachEvent but does not follow the script
            //script execution mode.
            if (node.attachEvent && !isOpera) {
                //Probably IE. IE (at least 6-8) do not fire
                //script onload right after executing the script, so
                //we cannot tie the anonymous define call to a name.
                //However, IE reports the script as being in "interactive"
                //readyState at the time of the define call.
                useInteractive = true;


                if (fetchOnlyFunction) {
                    //Need to use old school onreadystate here since
                    //when the event fires and the node is not attached
                    //to the DOM, the evt.srcElement is null, so use
                    //a closure to remember the node.
                    node.onreadystatechange = function (evt) {
                        //Script loaded but not executed.
                        //Clear loaded handler, set the real one that
                        //waits for script execution.
                        if (node.readyState === 'loaded') {
                            node.onreadystatechange = null;
                            node.attachEvent("onreadystatechange", callback);
                            fetchOnlyFunction(node);
                        }
                    };
                } else {
                    node.attachEvent("onreadystatechange", callback);
                }
            } else {
                node.addEventListener("load", callback, false);
            }
            node.src = url;

            //Fetch only means waiting to attach to DOM after loaded.
            if (!fetchOnlyFunction) {
                req.addScriptToDom(node);
            }

            return node;
        } else if (isWebWorker) {
            //In a web worker, use importScripts. This is not a very
            //efficient use of importScripts, importScripts will block until
            //its script is downloaded and evaluated. However, if web workers
            //are in play, the expectation that a build has been done so that
            //only one script needs to be loaded anyway. This may need to be
            //reevaluated if other use cases become common.
            importScripts(url);

            //Account for anonymous modules
            context.completeLoad(moduleName);
        }
        return null;
    };