The source code

    /**
     * @class Ext.ComponentMgr
     * <p>Provides a registry of all Components (instances of {@link Ext.Component} or any subclass
     * thereof) on a page so that they can be easily accessed by {@link Ext.Component component}
     * {@link Ext.Component#id id} (see {@link #get}, or the convenience method {@link Ext#getCmp Ext.getCmp}).</p>
     * <p>This object also provides a registry of available Component <i>classes</i>
     * indexed by a mnemonic code known as the Component's {@link Ext.Component#xtype xtype}.
     * The <code>{@link Ext.Component#xtype xtype}</code> provides a way to avoid instantiating child Components
     * when creating a full, nested config object for a complete Ext page.</p>
     * <p>A child Component may be specified simply as a <i>config object</i>
     * as long as the correct <code>{@link Ext.Component#xtype xtype}</code> is specified so that if and when the Component
     * needs rendering, the correct type can be looked up for lazy instantiation.</p>
     * <p>For a list of all available <code>{@link Ext.Component#xtype xtypes}</code>, see {@link Ext.Component}.</p>
     * @singleton
     */
    Ext.ComponentMgr = function(){
        var all = new Ext.util.MixedCollection();
        var types = {};
        var ptypes = {};

        return {
            /**
             * Registers a component.
             * @param {Ext.Component} c The component
             */
            register : function(c){
                all.add(c);
            },

            /**
             * Unregisters a component.
             * @param {Ext.Component} c The component
             */
            unregister : function(c){
                all.remove(c);
            },

            /**
             * Returns a component by {@link Ext.Component#id id}.
             * For additional details see {@link Ext.util.MixedCollection#get}.
             * @param {String} id The component {@link Ext.Component#id id}
             * @return Ext.Component The Component, <code>undefined</code> if not found, or <code>null</code> if a
             * Class was found.
             */
            get : function(id){
                return all.get(id);
            },

            /**
             * Registers a function that will be called when a Component with the specified id is added to ComponentMgr. This will happen on instantiation.
             * @param {String} id The component {@link Ext.Component#id id}
             * @param {Function} fn The callback function
             * @param {Object} scope The scope (<code>this</code> reference) in which the callback is executed. Defaults to the Component.
             */
            onAvailable : function(id, fn, scope){
                all.on("add", function(index, o){
                    if(o.id == id){
                        fn.call(scope || o, o);
                        all.un("add", fn, scope);
                    }
                });
            },

            /**
             * The MixedCollection used internally for the component cache. An example usage may be subscribing to
             * events on the MixedCollection to monitor addition or removal.  Read-only.
             * @type {MixedCollection}
             */
            all : all,

            /**
             * The xtypes that have been registered with the component manager.
             * @type {Object}
             */
            types : types,

            /**
             * The ptypes that have been registered with the component manager.
             * @type {Object}
             */
            ptypes: ptypes,

            /**
             * Checks if a Component type is registered.
             * @param {Ext.Component} xtype The mnemonic string by which the Component class may be looked up
             * @return {Boolean} Whether the type is registered.
             */
            isRegistered : function(xtype){
                return types[xtype] !== undefined;
            },

            /**
             * Checks if a Plugin type is registered.
             * @param {Ext.Component} ptype The mnemonic string by which the Plugin class may be looked up
             * @return {Boolean} Whether the type is registered.
             */
            isPluginRegistered : function(ptype){
                return ptypes[ptype] !== undefined;
            },

            /**
             * <p>Registers a new Component constructor, keyed by a new
             * {@link Ext.Component#xtype}.</p>
             * <p>Use this method (or its alias {@link Ext#reg Ext.reg}) to register new
             * subclasses of {@link Ext.Component} so that lazy instantiation may be used when specifying
             * child Components.
             * see {@link Ext.Container#items}</p>
             * @param {String} xtype The mnemonic string by which the Component class may be looked up.
             * @param {Constructor} cls The new Component class.
             */
            registerType : function(xtype, cls){
                types[xtype] = cls;
                cls.xtype = xtype;
            },

            /**
             * Creates a new Component from the specified config object using the
             * config object's {@link Ext.component#xtype xtype} to determine the class to instantiate.
             * @param {Object} config A configuration object for the Component you wish to create.
             * @param {Constructor} defaultType The constructor to provide the default Component type if
             * the config object does not contain a <code>xtype</code>. (Optional if the config contains a <code>xtype</code>).
             * @return {Ext.Component} The newly instantiated Component.
             */
            create : function(config, defaultType){
                return config.render ? config : new types[config.xtype || defaultType](config);
            },

            /**
             * <p>Registers a new Plugin constructor, keyed by a new
             * {@link Ext.Component#ptype}.</p>
             * <p>Use this method (or its alias {@link Ext#preg Ext.preg}) to register new
             * plugins for {@link Ext.Component}s so that lazy instantiation may be used when specifying
             * Plugins.</p>
             * @param {String} ptype The mnemonic string by which the Plugin class may be looked up.
             * @param {Constructor} cls The new Plugin class.
             */
            registerPlugin : function(ptype, cls){
                ptypes[ptype] = cls;
                cls.ptype = ptype;
            },

            /**
             * Creates a new Plugin from the specified config object using the
             * config object's {@link Ext.component#ptype ptype} to determine the class to instantiate.
             * @param {Object} config A configuration object for the Plugin you wish to create.
             * @param {Constructor} defaultType The constructor to provide the default Plugin type if
             * the config object does not contain a <code>ptype</code>. (Optional if the config contains a <code>ptype</code>).
             * @return {Ext.Component} The newly instantiated Plugin.
             */
            createPlugin : function(config, defaultType){
                var PluginCls = ptypes[config.ptype || defaultType];
                if (PluginCls.init) {
                    return PluginCls;
                } else {
                    return new PluginCls(config);
                }
            }
        };
    }();

    /**
     * Shorthand for {@link Ext.ComponentMgr#registerType}
     * @param {String} xtype The {@link Ext.component#xtype mnemonic string} by which the Component class
     * may be looked up.
     * @param {Constructor} cls The new Component class.
     * @member Ext
     * @method reg
     */
    Ext.reg = Ext.ComponentMgr.registerType; // this will be called a lot internally, shorthand to keep the bytes down
    /**
     * Shorthand for {@link Ext.ComponentMgr#registerPlugin}
     * @param {String} ptype The {@link Ext.component#ptype mnemonic string} by which the Plugin class
     * may be looked up.
     * @param {Constructor} cls The new Plugin class.
     * @member Ext
     * @method preg
     */
    Ext.preg = Ext.ComponentMgr.registerPlugin;
    /**
     * Shorthand for {@link Ext.ComponentMgr#create}
     * Creates a new Component from the specified config object using the
     * config object's {@link Ext.component#xtype xtype} to determine the class to instantiate.
     * @param {Object} config A configuration object for the Component you wish to create.
     * @param {Constructor} defaultType The constructor to provide the default Component type if
     * the config object does not contain a <code>xtype</code>. (Optional if the config contains a <code>xtype</code>).
     * @return {Ext.Component} The newly instantiated Component.
     * @member Ext
     * @method create
     */
    Ext.create = Ext.ComponentMgr.create;