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.

     * Usage:

     *
     * 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");
     *

     * // 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);
     *

     * // short handed call directly from the element object
     * Ext.get("foo").load({
            url: "bar.php",
            scripts: true,
            params: "param1=foo&param2=bar",
            text: "Loading Foo..."
     * });
     *
     * @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 asynchronous request, updating this element with the response.
    	     * If params are specified it uses POST, otherwise it uses GET.

    	     * Note: 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 update event handler.
    	     * @param {Object} options A config object containing any of the following options:
    	     * url : String/FunctionThe URL to request or a function which
    	     * returns the URL (defaults to the value of {@link Ext.Ajax#url} if not specified).
    	     * method : StringThe HTTP method to
    	     * use. Defaults to POST if the params argument is present, otherwise GET.
    	     * params : String/Object/FunctionThe
    	     * 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.
    	     * scripts : BooleanIf true
    	     * any <script> 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 after the execution of the scripts.
    	     * callback : FunctionA function to
    	     * be called when the response from the server arrives. The following
    	     * parameters are passed:
    	     * el : Ext.ElementThe Element being updated.
    	     * success : BooleanTrue for success, false for failure.
    	     * response : XMLHttpRequestThe XMLHttpRequest which processed the update.
    	     * options : ObjectThe config object passed to the update call.
    	     *
    	     * scope : ObjectThe scope in which
    	     * to execute the callback (The callback's this reference.) If the
    	     * params argument is a function, this scope is used for that function also.
    	     * discardUrl : BooleanBy 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 discardUrl:true (defaults to false).
    	     * timeout : NumberThe number of seconds to wait for a response before
    	     * timing out (defaults to {@link Ext.Updater.defaults#timeout}).
    	     * text : StringThe 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.
    	     * nocache : BooleanOnly 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}).
    	     *
    	     * For example:

    	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.
    	});

    	     */
    	    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 = ''+cfg.text+"";};
    	                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);
    	        }
    	    },

    		/**
    	     * Performs an async form post, updating this element with the response. If the form has the attribute
    	     * enctype="multipart/form-data", it assumes it's a file upload.
    	     * Uses this.sslBlankUrl for SSL file uploads to prevent IE security warning.
    	     * File uploads are not performed using normal "Ajax" techniques, that is they are not
    	     * performed using XMLHttpRequests. Instead the form is submitted in the standard manner with the
    	     * DOM <form> element temporarily modified to have its
    	     * target set to refer
    	     * to a dynamically generated, hidden <iframe> which is inserted into the document
    	     * but removed after the return data has been gathered.
    	     * Be aware that file upload packets, sent with the content type multipart/form-data
    	     * and some server technologies (notably JEE) may require some custom processing in order to
    	     * retrieve parameter names and parameter values from the packet content.
    	     * @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:
    	     * el : Ext.ElementThe Element being updated.
    	     * success : BooleanTrue for success, false for failure.
    	     * response : XMLHttpRequestThe XMLHttpRequest which processed the update.
    	     */
    	    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
    	     * "¶m1=1¶m2=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 '<div class="loading-indicator">Loading...</div>').
         * @type String
         */
        indicatorText : 'Loading...',
         /**
         * 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 || "javascript:false")
    };

    /**
     * Static convenience method. This method is deprecated in favor of el.load({url:'foo.php', ...}).
     * Usage:
     * Ext.Updater.updateElement("my-div", "stuff.php");
     * @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
     * Default Content renderer. Updates the elements innerHTML with the responseText.
     */
    Ext.Updater.BasicRenderer = function(){};

    Ext.Updater.BasicRenderer.prototype = {
        /**
         * This is called when the transaction is completed and it's time to update the element - The BasicRenderer
         * updates the elements innerHTML with the responseText - To perform a custom render (i.e. XML or JSON processing),
         * create an object with a "render(el, response)" method and pass it to setRenderer on the Updater.
         * @param {Ext.Element} el The element being rendered
         * @param {Object} response 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);
        }
    };