The source code

    /**
     * @class Ext.Updater
     * @extends Ext.util.Observable
     * Provides AJAX-style update capabilities for Element objects.  Updater can be used to {@link #update}
     * an {@link Ext.Element} once, or you can use {@link #startAutoRefresh} to set up an auto-updating
     * {@link Ext.Element Element} on a specific interval.<br><br>
     * Usage:<br>
     * <pre><code>
     * var el = Ext.get("foo"); // Get Ext.Element object
     * var mgr = el.getUpdater();
     * mgr.update({
            url: "http://myserver.com/index.php",
            params: {
                param1: "foo",
                param2: "bar"
            }
     * });
     * ...
     * mgr.formUpdate("myFormId", "http://myserver.com/index.php");
     * <br>
     * // or directly (returns the same Updater instance)
     * var mgr = new Ext.Updater("myElementId");
     * mgr.startAutoRefresh(60, "http://myserver.com/index.php");
     * mgr.on("update", myFcnNeedsToKnow);
     * <br>
     * // short handed call directly from the element object
     * Ext.get("foo").load({
            url: "bar.php",
            scripts: true,
            params: "param1=foo&amp;param2=bar",
            text: "Loading Foo..."
     * });
     * </code></pre>
     * @constructor
     * Create new Updater directly.
     * @param {Mixed} el The element to update
     * @param {Boolean} forceNew (optional) By default the constructor checks to see if the passed element already
     * has an Updater and if it does it returns the same instance. This will skip that check (useful for extending this class).
     */
    Ext.UpdateManager = Ext.Updater = Ext.extend(Ext.util.Observable,
    function() {
        var BEFOREUPDATE = "beforeupdate",
            UPDATE = "update",
            FAILURE = "failure";

        // private
        function processSuccess(response){
            var me = this;
            me.transaction = null;
            if (response.argument.form && response.argument.reset) {
                try { // put in try/catch since some older FF releases had problems with this
                    response.argument.form.reset();
                } catch(e){}
            }
            if (me.loadScripts) {
                me.renderer.render(me.el, response, me,
                   updateComplete.createDelegate(me, [response]));
            } else {
                me.renderer.render(me.el, response, me);
                updateComplete.call(me, response);
            }
        }

        // private
        function updateComplete(response, type, success){
            this.fireEvent(type || UPDATE, this.el, response);
            if(Ext.isFunction(response.argument.callback)){
                response.argument.callback.call(response.argument.scope, this.el, Ext.isEmpty(success) ? true : false, response, response.argument.options);
            }
        }

        // private
        function processFailure(response){
            updateComplete.call(this, response, FAILURE, !!(this.transaction = null));
        }

        return {
            constructor: function(el, forceNew){
                var me = this;
                el = Ext.get(el);
                if(!forceNew && el.updateManager){
                    return el.updateManager;
                }
                /**
                 * The Element object
                 * @type Ext.Element
                 */
                me.el = el;
                /**
                 * Cached url to use for refreshes. Overwritten every time update() is called unless "discardUrl" param is set to true.
                 * @type String
                 */
                me.defaultUrl = null;

                me.addEvents(
                    /**
                     * @event beforeupdate
                     * Fired before an update is made, return false from your handler and the update is cancelled.
                     * @param {Ext.Element} el
                     * @param {String/Object/Function} url
                     * @param {String/Object} params
                     */
                    BEFOREUPDATE,
                    /**
                     * @event update
                     * Fired after successful update is made.
                     * @param {Ext.Element} el
                     * @param {Object} oResponseObject The response Object
                     */
                    UPDATE,
                    /**
                     * @event failure
                     * Fired on update failure.
                     * @param {Ext.Element} el
                     * @param {Object} oResponseObject The response Object
                     */
                    FAILURE
                );

                Ext.apply(me, Ext.Updater.defaults);
                /**
                 * Blank page URL to use with SSL file uploads (defaults to {@link Ext.Updater.defaults#sslBlankUrl}).
                 * @property sslBlankUrl
                 * @type String
                 */
                /**
                 * Whether to append unique parameter on get request to disable caching (defaults to {@link Ext.Updater.defaults#disableCaching}).
                 * @property disableCaching
                 * @type Boolean
                 */
                /**
                 * Text for loading indicator (defaults to {@link Ext.Updater.defaults#indicatorText}).
                 * @property indicatorText
                 * @type String
                 */
                /**
                 * Whether to show indicatorText when loading (defaults to {@link Ext.Updater.defaults#showLoadIndicator}).
                 * @property showLoadIndicator
                 * @type String
                 */
                /**
                 * Timeout for requests or form posts in seconds (defaults to {@link Ext.Updater.defaults#timeout}).
                 * @property timeout
                 * @type Number
                 */
                /**
                 * True to process scripts in the output (defaults to {@link Ext.Updater.defaults#loadScripts}).
                 * @property loadScripts
                 * @type Boolean
                 */

                /**
                 * Transaction object of the current executing transaction, or null if there is no active transaction.
                 */
                me.transaction = null;
                /**
                 * Delegate for refresh() prebound to "this", use myUpdater.refreshDelegate.createCallback(arg1, arg2) to bind arguments
                 * @type Function
                 */
                me.refreshDelegate = me.refresh.createDelegate(me);
                /**
                 * Delegate for update() prebound to "this", use myUpdater.updateDelegate.createCallback(arg1, arg2) to bind arguments
                 * @type Function
                 */
                me.updateDelegate = me.update.createDelegate(me);
                /**
                 * Delegate for formUpdate() prebound to "this", use myUpdater.formUpdateDelegate.createCallback(arg1, arg2) to bind arguments
                 * @type Function
                 */
                me.formUpdateDelegate = (me.formUpdate || function(){}).createDelegate(me);

                /**
                 * The renderer for this Updater (defaults to {@link Ext.Updater.BasicRenderer}).
                 */
                me.renderer = me.renderer || me.getDefaultRenderer();

                Ext.Updater.superclass.constructor.call(me);
            },

            /**
             * Sets the content renderer for this Updater. See {@link Ext.Updater.BasicRenderer#render} for more details.
             * @param {Object} renderer The object implementing the render() method
             */
            setRenderer : function(renderer){
                this.renderer = renderer;
            },

            /**
             * Returns the current content renderer for this Updater. See {@link Ext.Updater.BasicRenderer#render} for more details.
             * @return {Object}
             */
            getRenderer : function(){
               return this.renderer;
            },

            /**
             * This is an overrideable method which returns a reference to a default
             * renderer class if none is specified when creating the Ext.Updater.
             * Defaults to {@link Ext.Updater.BasicRenderer}
             */
            getDefaultRenderer: function() {
                return new Ext.Updater.BasicRenderer();
            },

            /**
             * Sets the default URL used for updates.
             * @param {String/Function} defaultUrl The url or a function to call to get the url
             */
            setDefaultUrl : function(defaultUrl){
                this.defaultUrl = defaultUrl;
            },

            /**
             * Get the Element this Updater is bound to
             * @return {Ext.Element} The element
             */
            getEl : function(){
                return this.el;
            },

            /**
             * Performs an <b>asynchronous</b> request, updating this element with the response.
             * If params are specified it uses POST, otherwise it uses GET.<br><br>
             * <b>Note:</b> Due to the asynchronous nature of remote server requests, the Element
             * will not have been fully updated when the function returns. To post-process the returned
             * data, use the callback option, or an <b><code>update</code></b> event handler.
             * @param {Object} options A config object containing any of the following options:<ul>
             * <li>url : <b>String/Function</b><p class="sub-desc">The URL to request or a function which
             * <i>returns</i> the URL (defaults to the value of {@link Ext.Ajax#url} if not specified).</p></li>
             * <li>method : <b>String</b><p class="sub-desc">The HTTP method to
             * use. Defaults to POST if the <code>params</code> argument is present, otherwise GET.</p></li>
             * <li>params : <b>String/Object/Function</b><p class="sub-desc">The
             * parameters to pass to the server (defaults to none). These may be specified as a url-encoded
             * string, or as an object containing properties which represent parameters,
             * or as a function, which returns such an object.</p></li>
             * <li>scripts : <b>Boolean</b><p class="sub-desc">If <code>true</code>
             * any &lt;script&gt; tags embedded in the response text will be extracted
             * and executed (defaults to {@link Ext.Updater.defaults#loadScripts}). If this option is specified,
             * the callback will be called <i>after</i> the execution of the scripts.</p></li>
             * <li>callback : <b>Function</b><p class="sub-desc">A function to
             * be called when the response from the server arrives. The following
             * parameters are passed:<ul>
             * <li><b>el</b> : Ext.Element<p class="sub-desc">The Element being updated.</p></li>
             * <li><b>success</b> : Boolean<p class="sub-desc">True for success, false for failure.</p></li>
             * <li><b>response</b> : XMLHttpRequest<p class="sub-desc">The XMLHttpRequest which processed the update.</p></li>
             * <li><b>options</b> : Object<p class="sub-desc">The config object passed to the update call.</p></li></ul>
             * </p></li>
             * <li>scope : <b>Object</b><p class="sub-desc">The scope in which
             * to execute the callback (The callback's <code>this</code> reference.) If the
             * <code>params</code> argument is a function, this scope is used for that function also.</p></li>
             * <li>discardUrl : <b>Boolean</b><p class="sub-desc">By default, the URL of this request becomes
             * the default URL for this Updater object, and will be subsequently used in {@link #refresh}
             * calls.  To bypass this behavior, pass <code>discardUrl:true</code> (defaults to false).</p></li>
             * <li>timeout : <b>Number</b><p class="sub-desc">The number of seconds to wait for a response before
             * timing out (defaults to {@link Ext.Updater.defaults#timeout}).</p></li>
             * <li>text : <b>String</b><p class="sub-desc">The text to use as the innerHTML of the
             * {@link Ext.Updater.defaults#indicatorText} div (defaults to 'Loading...').  To replace the entire div, not
             * just the text, override {@link Ext.Updater.defaults#indicatorText} directly.</p></li>
             * <li>nocache : <b>Boolean</b><p class="sub-desc">Only needed for GET
             * requests, this option causes an extra, auto-generated parameter to be appended to the request
             * to defeat caching (defaults to {@link Ext.Updater.defaults#disableCaching}).</p></li></ul>
             * <p>
             * For example:
        <pre><code>
        um.update({
            url: "your-url.php",
            params: {param1: "foo", param2: "bar"}, // or a URL encoded string
            callback: yourFunction,
            scope: yourObject, //(optional scope)
            discardUrl: true,
            nocache: true,
            text: "Loading...",
            timeout: 60,
            scripts: false // Save time by avoiding RegExp execution.
        });
        </code></pre>
             */
            update : function(url, params, callback, discardUrl){
                var me = this,
                    cfg,
                    callerScope;

                if(me.fireEvent(BEFOREUPDATE, me.el, url, params) !== false){
                    if(Ext.isObject(url)){ // must be config object
                        cfg = url;
                        url = cfg.url;
                        params = params || cfg.params;
                        callback = callback || cfg.callback;
                        discardUrl = discardUrl || cfg.discardUrl;
                        callerScope = cfg.scope;
                        if(!Ext.isEmpty(cfg.nocache)){me.disableCaching = cfg.nocache;};
                        if(!Ext.isEmpty(cfg.text)){me.indicatorText = '<div class="loading-indicator">'+cfg.text+"</div>";};
                        if(!Ext.isEmpty(cfg.scripts)){me.loadScripts = cfg.scripts;};
                        if(!Ext.isEmpty(cfg.timeout)){me.timeout = cfg.timeout;};
                    }
                    me.showLoading();

                    if(!discardUrl){
                        me.defaultUrl = url;
                    }
                    if(Ext.isFunction(url)){
                        url = url.call(me);
                    }

                    var o = Ext.apply({}, {
                        url : url,
                        params: (Ext.isFunction(params) && callerScope) ? params.createDelegate(callerScope) : params,
                        success: processSuccess,
                        failure: processFailure,
                        scope: me,
                        callback: undefined,
                        timeout: (me.timeout*1000),
                        disableCaching: me.disableCaching,
                        argument: {
                            "options": cfg,
                            "url": url,
                            "form": null,
                            "callback": callback,
                            "scope": callerScope || window,
                            "params": params
                        }
                    }, cfg);

                    me.transaction = Ext.Ajax.request(o);
                }
            },

            /**
             * <p>Performs an asynchronous form post, updating this element with the response. If the form has the attribute
             * enctype="<a href="http://www.faqs.org/rfcs/rfc2388.html">multipart/form-data</a>", it assumes it's a file upload.
             * Uses this.sslBlankUrl for SSL file uploads to prevent IE security warning.</p>
             * <p>File uploads are not performed using normal "Ajax" techniques, that is they are <b>not</b>
             * performed using XMLHttpRequests. Instead the form is submitted in the standard manner with the
             * DOM <code>&lt;form></code> element temporarily modified to have its
             * <a href="http://www.w3.org/TR/REC-html40/present/frames.html#adef-target">target</a> set to refer
             * to a dynamically generated, hidden <code>&lt;iframe></code> which is inserted into the document
             * but removed after the return data has been gathered.</p>
             * <p>Be aware that file upload packets, sent with the content type <a href="http://www.faqs.org/rfcs/rfc2388.html">multipart/form-data</a>
             * and some server technologies (notably JEE) may require some custom processing in order to
             * retrieve parameter names and parameter values from the packet content.</p>
             * @param {String/HTMLElement} form The form Id or form element
             * @param {String} url (optional) The url to pass the form to. If omitted the action attribute on the form will be used.
             * @param {Boolean} reset (optional) Whether to try to reset the form after the update
             * @param {Function} callback (optional) Callback when transaction is complete. The following
             * parameters are passed:<ul>
             * <li><b>el</b> : Ext.Element<p class="sub-desc">The Element being updated.</p></li>
             * <li><b>success</b> : Boolean<p class="sub-desc">True for success, false for failure.</p></li>
             * <li><b>response</b> : XMLHttpRequest<p class="sub-desc">The XMLHttpRequest which processed the update.</p></li></ul>
             */
            formUpdate : function(form, url, reset, callback){
                var me = this;
                if(me.fireEvent(BEFOREUPDATE, me.el, form, url) !== false){
                    if(Ext.isFunction(url)){
                        url = url.call(me);
                    }
                    form = Ext.getDom(form);
                    me.transaction = Ext.Ajax.request({
                        form: form,
                        url:url,
                        success: processSuccess,
                        failure: processFailure,
                        scope: me,
                        timeout: (me.timeout*1000),
                        argument: {
                            "url": url,
                            "form": form,
                            "callback": callback,
                            "reset": reset
                        }
                    });
                    me.showLoading.defer(1, me);
                }
            },

            /**
             * Set this element to auto refresh.  Can be canceled by calling {@link #stopAutoRefresh}.
             * @param {Number} interval How often to update (in seconds).
             * @param {String/Object/Function} url (optional) The url for this request, a config object in the same format
             * supported by {@link #load}, or a function to call to get the url (defaults to the last used url).  Note that while
             * the url used in a load call can be reused by this method, other load config options will not be reused and must be
             * sepcified as part of a config object passed as this paramter if needed.
             * @param {String/Object} params (optional) The parameters to pass as either a url encoded string
             * "&param1=1&param2=2" or as an object {param1: 1, param2: 2}
             * @param {Function} callback (optional) Callback when transaction is complete - called with signature (oElement, bSuccess)
             * @param {Boolean} refreshNow (optional) Whether to execute the refresh now, or wait the interval
             */
            startAutoRefresh : function(interval, url, params, callback, refreshNow){
                var me = this;
                if(refreshNow){
                    me.update(url || me.defaultUrl, params, callback, true);
                }
                if(me.autoRefreshProcId){
                    clearInterval(me.autoRefreshProcId);
                }
                me.autoRefreshProcId = setInterval(me.update.createDelegate(me, [url || me.defaultUrl, params, callback, true]), interval * 1000);
            },

            /**
             * Stop auto refresh on this element.
             */
            stopAutoRefresh : function(){
                if(this.autoRefreshProcId){
                    clearInterval(this.autoRefreshProcId);
                    delete this.autoRefreshProcId;
                }
            },

            /**
             * Returns true if the Updater is currently set to auto refresh its content (see {@link #startAutoRefresh}), otherwise false.
             */
            isAutoRefreshing : function(){
               return !!this.autoRefreshProcId;
            },

            /**
             * Display the element's "loading" state. By default, the element is updated with {@link #indicatorText}. This
             * method may be overridden to perform a custom action while this Updater is actively updating its contents.
             */
            showLoading : function(){
                if(this.showLoadIndicator){
                    this.el.dom.innerHTML = this.indicatorText;
                }
            },

            /**
             * Aborts the currently executing transaction, if any.
             */
            abort : function(){
                if(this.transaction){
                    Ext.Ajax.abort(this.transaction);
                }
            },

            /**
             * Returns true if an update is in progress, otherwise false.
             * @return {Boolean}
             */
            isUpdating : function(){
                return this.transaction ? Ext.Ajax.isLoading(this.transaction) : false;
            },

            /**
             * Refresh the element with the last used url or defaultUrl. If there is no url, it returns immediately
             * @param {Function} callback (optional) Callback when transaction is complete - called with signature (oElement, bSuccess)
             */
            refresh : function(callback){
                if(this.defaultUrl){
                    this.update(this.defaultUrl, null, callback, true);
                }
            }
        };
    }());

    /**
     * @class Ext.Updater.defaults
     * The defaults collection enables customizing the default properties of Updater
     */
    Ext.Updater.defaults = {
       /**
         * Timeout for requests or form posts in seconds (defaults to 30 seconds).
         * @type Number
         */
        timeout : 30,
        /**
         * True to append a unique parameter to GET requests to disable caching (defaults to false).
         * @type Boolean
         */
        disableCaching : false,
        /**
         * Whether or not to show {@link #indicatorText} during loading (defaults to true).
         * @type Boolean
         */
        showLoadIndicator : true,
        /**
         * Text for loading indicator (defaults to '&lt;div class="loading-indicator"&gt;Loading...&lt;/div&gt;').
         * @type String
         */
        indicatorText : '<div class="loading-indicator">Loading...</div>',
         /**
         * True to process scripts by default (defaults to false).
         * @type Boolean
         */
        loadScripts : false,
        /**
        * Blank page URL to use with SSL file uploads (defaults to {@link Ext#SSL_SECURE_URL} if set, or "javascript:false").
        * @type String
        */
        sslBlankUrl : Ext.SSL_SECURE_URL
    };

    /**
     * Static convenience method. <b>This method is deprecated in favor of el.load({url:'foo.php', ...})</b>.
     * Usage:
     * <pre><code>Ext.Updater.updateElement("my-div", "stuff.php");</code></pre>
     * @param {Mixed} el The element to update
     * @param {String} url The url
     * @param {String/Object} params (optional) Url encoded param string or an object of name/value pairs
     * @param {Object} options (optional) A config object with any of the Updater properties you want to set - for
     * example: {disableCaching:true, indicatorText: "Loading data..."}
     * @static
     * @deprecated
     * @member Ext.Updater
     */
    Ext.Updater.updateElement = function(el, url, params, options){
        var um = Ext.get(el).getUpdater();
        Ext.apply(um, options);
        um.update(url, params, options ? options.callback : null);
    };

    /**
     * @class Ext.Updater.BasicRenderer
     * <p>This class is a base class implementing a simple render method which updates an element using results from an Ajax request.</p>
     * <p>The BasicRenderer updates the element's innerHTML with the responseText. To perform a custom render (i.e. XML or JSON processing),
     * create an object with a conforming {@link #render} method and pass it to setRenderer on the Updater.</p>
     */
    Ext.Updater.BasicRenderer = function(){};

    Ext.Updater.BasicRenderer.prototype = {
        /**
         * This method is called when an Ajax response is received, and an Element needs updating.
         * @param {Ext.Element} el The element being rendered
         * @param {Object} xhr The XMLHttpRequest object
         * @param {Updater} updateManager The calling update manager
         * @param {Function} callback A callback that will need to be called if loadScripts is true on the Updater
         */
         render : function(el, response, updateManager, callback){
            el.update(response.responseText, updateManager.loadScripts, callback);
        }
    };