The source code

    /**
     * @class Ext.CompositeElement
     * @extends Ext.CompositeElementLite
     * Standard composite class. Creates a Ext.Element for every element in the collection.
     *

     * NOTE: Although they are not listed, this class supports all of the set/update methods of Ext.Element. All Ext.Element
     * actions will be performed on all the elements in this collection.
     *

     * All methods return this and can be chained.

     var els = Ext.select("#some-el div.some-class", true);
     // or select directly from an existing element
     var el = Ext.get('some-el');
     el.select('div.some-class', true);

     els.setWidth(100); // all elements become 100 width
     els.hide(true); // all elements fade out and hide
     // or
     els.setWidth(100).hide(true);

     */
    Ext.CompositeElement = function(els, root){
        this.elements = [];
        this.add(els, root);
    };

    Ext.extend(Ext.CompositeElement, Ext.CompositeElementLite, {
        invoke : function(fn, args){
    	    Ext.each(this.elements, function(e) {
            	Ext.Element.prototype[fn].apply(e, args);
            });
            return this;
        },

        /**
        * Adds elements to this composite.
        * @param {String/Array} els A string CSS selector, an array of elements or an element
        * @return {CompositeElement} this
        */
        add : function(els, root){
    	    if(!els){
                return this;
            }
            if(typeof els == "string"){
                els = Ext.Element.selectorFunction(els, root);
            }
            var yels = this.elements;
    	    Ext.each(els, function(e) {
            	yels.push(Ext.get(e));
            });
            return this;
        },

        /**
         * Returns the Element object at the specified index
         * @param {Number} index
         * @return {Ext.Element}
         */
        item : function(index){
            return this.elements[index] || null;
        },

        indexOf : function(el){
            return this.elements.indexOf(Ext.get(el));
        },

        filter : function(selector){
    		var me = this,
    			out = [];

    		Ext.each(me.elements, function(el) {
    			if(el.is(selector)){
    				out.push(Ext.get(el));
    			}
    		});
    		me.elements = out;
    		return me;
    	},

    	/**
        * Calls the passed function passing (el, this, index) for each element in this composite.
        * @param {Function} fn The function to call
        * @param {Object} scope (optional) The this object (defaults to the element)
        * @return {CompositeElement} this
        */
        each : function(fn, scope){
            Ext.each(this.elements, function(e,i) {
    	        return fn.call(scope || e, e, this, i);
            }, this);
            return this;
        }
    });

    /**
     * Selects elements based on the passed CSS selector to enable {@link Ext.Element Element} methods
     * to be applied to many related elements in one statement through the returned {@link Ext.CompositeElement CompositeElement} or
     * {@link Ext.CompositeElementLite CompositeElementLite} object.
     * @param {String/Array} selector The CSS selector or an array of elements
     * @param {Boolean} unique (optional) true to create a unique Ext.Element for each element (defaults to a shared flyweight object)
     * @param {HTMLElement/String} root (optional) The root element of the query or id of the root
     * @return {CompositeElementLite/CompositeElement}
     * @member Ext.Element
     * @method select
     */
    Ext.Element.select = function(selector, unique, root){
        var els;
        if(typeof selector == "string"){
            els = Ext.Element.selectorFunction(selector, root);
        }else if(selector.length !== undefined){
            els = selector;
        }else{
            throw "Invalid selector";
        }

        return (unique === true) ? new Ext.CompositeElement(els) : new Ext.CompositeElementLite(els);
    };

    /**
     * Selects elements based on the passed CSS selector to enable {@link Ext.Element Element} methods
     * to be applied to many related elements in one statement through the returned {@link Ext.CompositeElement CompositeElement} or
     * {@link Ext.CompositeElementLite CompositeElementLite} object.
     * @param {String/Array} selector The CSS selector or an array of elements
     * @param {Boolean} unique (optional) true to create a unique Ext.Element for each element (defaults to a shared flyweight object)
     * @param {HTMLElement/String} root (optional) The root element of the query or id of the root
     * @return {CompositeElementLite/CompositeElement}
     * @member Ext.Element
     * @method select
     */
    Ext.select = Ext.Element.select;