The source code

    /**
     * @class Ext.CompositeElementLite
     * Flyweight composite class. Reuses the same Ext.Element for element operations.

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

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

     * 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.
     */
    Ext.CompositeElementLite = function(els, root){
        this.elements = [];
        this.add(els, root);
        this.el = new Ext.Element.Flyweight();
    };

    Ext.CompositeElementLite.prototype = {
    	isComposite: true,
    	/**
         * Returns the number of elements in this composite
         * @return Number
         */
        getCount : function(){
            return this.elements.length;
        },
    	add : function(els){
            if(els){
                if (Ext.isArray(els)) {
                    this.elements = this.elements.concat(els);
                } else {
                    var yels = this.elements;
    	            Ext.each(els, function(e) {
                        yels.push(e);
                    });
                }
            }
            return this;
        },
        invoke : function(fn, args){
            var els = this.elements,
            	el = this.el;
    	    Ext.each(els, function(e) {
                el.dom = e;
            	Ext.Element.prototype[fn].apply(el, args);
            });
            return this;
        },
        /**
         * Returns a flyweight Element of the dom element object at the specified index
         * @param {Number} index
         * @return {Ext.Element}
         */
        item : function(index){
    	    var me = this;
            if(!me.elements[index]){
                return null;
            }
            me.el.dom = me.elements[index];
            return me.el;
        },

        // fixes scope with flyweight
        addListener : function(eventName, handler, scope, opt){
            Ext.each(this.elements, function(e) {
    	        Ext.EventManager.on(e, eventName, handler, scope || e, opt);
            });
            return this;
        },
        /**
        * Calls the passed function passing (el, this, index) for each element in this composite. The element
        * passed is the flyweight (shared) Ext.Element instance, so if you require a
        * a reference to the dom node, use el.dom.
        * @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){
            var me = this,
            	el = me.el;

    	    Ext.each(me.elements, function(e,i) {
                el.dom = e;
            	return fn.call(scope || el, el, me, i);
            });
            return me;
        },

        /**
         * Find the index of the passed element within the composite collection.
         * @param el {Mixed} The id of an element, or an Ext.Element, or an HtmlElement to find within the composite collection.
         * @return Number The index of the passed Ext.Element in the composite collection, or -1 if not found.
         */
        indexOf : function(el){
            return this.elements.indexOf(Ext.getDom(el));
        },

        /**
        * Replaces the specified element with the passed element.
        * @param {Mixed} el The id of an element, the Element itself, the index of the element in this composite
        * to replace.
        * @param {Mixed} replacement The id of an element or the Element itself.
        * @param {Boolean} domReplace (Optional) True to remove and replace the element in the document too.
        * @return {CompositeElement} this
        */
        replaceElement : function(el, replacement, domReplace){
            var index = !isNaN(el) ? el : this.indexOf(el),
            	d;
            if(index > -1){
                replacement = Ext.getDom(replacement);
                if(domReplace){
                    d = this.elements[index];
                    d.parentNode.insertBefore(replacement, d);
                    Ext.removeNode(d);
                }
                this.elements.splice(index, 1, replacement);
            }
            return this;
        },

        /**
         * Removes all elements.
         */
        clear : function(){
            this.elements = [];
        }
    };

    Ext.CompositeElementLite.prototype.on = Ext.CompositeElementLite.prototype.addListener;

    (function(){
    var fnName,
    	ElProto = Ext.Element.prototype,
    	CelProto = Ext.CompositeElementLite.prototype;

    for(fnName in ElProto){
        if(Ext.isFunction(ElProto[fnName])){
    	    (function(fnName){
    		    CelProto[fnName] = CelProto[fnName] || function(){
    		    	return this.invoke(fnName, arguments);
    	    	};
        	}).call(CelProto, fnName);

        }
    }
    })();

    if(Ext.DomQuery){
        Ext.Element.selectorFunction = Ext.DomQuery.select;
    }

    /**
     * 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) Not supported in core
     * @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 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
     * @method select
     */
    Ext.select = Ext.Element.select;