The source code

    /**
     * @class Ext.util.MixedCollection
     * @extends Ext.util.Observable
     * A Collection class that maintains both numeric indexes and keys and exposes events.
     * @constructor
     * @param {Boolean} allowFunctions Specify <tt>true</tt> if the {@link #addAll}
     * function should add function references to the collection. Defaults to
     * <tt>false</tt>.
     * @param {Function} keyFn A function that can accept an item of the type(s) stored in this MixedCollection
     * and return the key value for that item.  This is used when available to look up the key on items that
     * were passed without an explicit key parameter to a MixedCollection method.  Passing this parameter is
     * equivalent to providing an implementation for the {@link #getKey} method.
     */
    Ext.util.MixedCollection = function(allowFunctions, keyFn){
        this.items = [];
        this.map = {};
        this.keys = [];
        this.length = 0;
        this.addEvents(
            /**
             * @event clear
             * Fires when the collection is cleared.
             */
            'clear',
            /**
             * @event add
             * Fires when an item is added to the collection.
             * @param {Number} index The index at which the item was added.
             * @param {Object} o The item added.
             * @param {String} key The key associated with the added item.
             */
            'add',
            /**
             * @event replace
             * Fires when an item is replaced in the collection.
             * @param {String} key he key associated with the new added.
             * @param {Object} old The item being replaced.
             * @param {Object} new The new item.
             */
            'replace',
            /**
             * @event remove
             * Fires when an item is removed from the collection.
             * @param {Object} o The item being removed.
             * @param {String} key (optional) The key associated with the removed item.
             */
            'remove',
            'sort'
        );
        this.allowFunctions = allowFunctions === true;
        if(keyFn){
            this.getKey = keyFn;
        }
        Ext.util.MixedCollection.superclass.constructor.call(this);
    };

    Ext.extend(Ext.util.MixedCollection, Ext.util.Observable, {

        /**
         * @cfg {Boolean} allowFunctions Specify <tt>true</tt> if the {@link #addAll}
         * function should add function references to the collection. Defaults to
         * <tt>false</tt>.
         */
        allowFunctions : false,

        /**
         * Adds an item to the collection. Fires the {@link #add} event when complete.
         * @param {String} key <p>The key to associate with the item, or the new item.</p>
         * <p>If a {@link #getKey} implementation was specified for this MixedCollection,
         * or if the key of the stored items is in a property called <tt><b>id</b></tt>,
         * the MixedCollection will be able to <i>derive</i> the key for the new item.
         * In this case just pass the new item in this parameter.</p>
         * @param {Object} o The item to add.
         * @return {Object} The item added.
         */
        add : function(key, o){
            if(arguments.length == 1){
                o = arguments[0];
                key = this.getKey(o);
            }
            if(typeof key != 'undefined' && key !== null){
                var old = this.map[key];
                if(typeof old != 'undefined'){
                    return this.replace(key, o);
                }
                this.map[key] = o;
            }
            this.length++;
            this.items.push(o);
            this.keys.push(key);
            this.fireEvent('add', this.length-1, o, key);
            return o;
        },

        /**
          * MixedCollection has a generic way to fetch keys if you implement getKey.  The default implementation
          * simply returns <b><code>item.id</code></b> but you can provide your own implementation
          * to return a different value as in the following examples:<pre><code>
    // normal way
    var mc = new Ext.util.MixedCollection();
    mc.add(someEl.dom.id, someEl);
    mc.add(otherEl.dom.id, otherEl);
    //and so on

    // using getKey
    var mc = new Ext.util.MixedCollection();
    mc.getKey = function(el){
       return el.dom.id;
    };
    mc.add(someEl);
    mc.add(otherEl);

    // or via the constructor
    var mc = new Ext.util.MixedCollection(false, function(el){
       return el.dom.id;
    });
    mc.add(someEl);
    mc.add(otherEl);
         * </code></pre>
         * @param {Object} item The item for which to find the key.
         * @return {Object} The key for the passed item.
         */
        getKey : function(o){
             return o.id;
        },

        /**
         * Replaces an item in the collection. Fires the {@link #replace} event when complete.
         * @param {String} key <p>The key associated with the item to replace, or the replacement item.</p>
         * <p>If you supplied a {@link #getKey} implementation for this MixedCollection, or if the key
         * of your stored items is in a property called <tt><b>id</b></tt>, then the MixedCollection
         * will be able to <i>derive</i> the key of the replacement item. If you want to replace an item
         * with one having the same key value, then just pass the replacement item in this parameter.</p>
         * @param o {Object} o (optional) If the first parameter passed was a key, the item to associate
         * with that key.
         * @return {Object}  The new item.
         */
        replace : function(key, o){
            if(arguments.length == 1){
                o = arguments[0];
                key = this.getKey(o);
            }
            var old = this.map[key];
            if(typeof key == 'undefined' || key === null || typeof old == 'undefined'){
                 return this.add(key, o);
            }
            var index = this.indexOfKey(key);
            this.items[index] = o;
            this.map[key] = o;
            this.fireEvent('replace', key, old, o);
            return o;
        },

        /**
         * Adds all elements of an Array or an Object to the collection.
         * @param {Object/Array} objs An Object containing properties which will be added
         * to the collection, or an Array of values, each of which are added to the collection.
         * Functions references will be added to the collection if <code>{@link #allowFunctions}</code>
         * has been set to <tt>true</tt>.
         */
        addAll : function(objs){
            if(arguments.length > 1 || Ext.isArray(objs)){
                var args = arguments.length > 1 ? arguments : objs;
                for(var i = 0, len = args.length; i < len; i++){
                    this.add(args[i]);
                }
            }else{
                for(var key in objs){
                    if(this.allowFunctions || typeof objs[key] != 'function'){
                        this.add(key, objs[key]);
                    }
                }
            }
        },

        /**
         * Executes the specified function once for every item in the collection, passing the following arguments:
         * <div class="mdetail-params"><ul>
         * <li><b>item</b> : Mixed<p class="sub-desc">The collection item</p></li>
         * <li><b>index</b> : Number<p class="sub-desc">The item's index</p></li>
         * <li><b>length</b> : Number<p class="sub-desc">The total number of items in the collection</p></li>
         * </ul></div>
         * The function should return a boolean value. Returning false from the function will stop the iteration.
         * @param {Function} fn The function to execute for each item.
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the function is executed. Defaults to the current item in the iteration.
         */
        each : function(fn, scope){
            var items = [].concat(this.items); // each safe for removal
            for(var i = 0, len = items.length; i < len; i++){
                if(fn.call(scope || items[i], items[i], i, len) === false){
                    break;
                }
            }
        },

        /**
         * Executes the specified function once for every key in the collection, passing each
         * key, and its associated item as the first two parameters.
         * @param {Function} fn The function to execute for each item.
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the function is executed. Defaults to the browser window.
         */
        eachKey : function(fn, scope){
            for(var i = 0, len = this.keys.length; i < len; i++){
                fn.call(scope || window, this.keys[i], this.items[i], i, len);
            }
        },

        /**
         * Returns the first item in the collection which elicits a true return value from the
         * passed selection function.
         * @param {Function} fn The selection function to execute for each item.
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the function is executed. Defaults to the browser window.
         * @return {Object} The first item in the collection which returned true from the selection function.
         */
        find : function(fn, scope){
            for(var i = 0, len = this.items.length; i < len; i++){
                if(fn.call(scope || window, this.items[i], this.keys[i])){
                    return this.items[i];
                }
            }
            return null;
        },

        /**
         * Inserts an item at the specified index in the collection. Fires the {@link #add} event when complete.
         * @param {Number} index The index to insert the item at.
         * @param {String} key The key to associate with the new item, or the item itself.
         * @param {Object} o (optional) If the second parameter was a key, the new item.
         * @return {Object} The item inserted.
         */
        insert : function(index, key, o){
            if(arguments.length == 2){
                o = arguments[1];
                key = this.getKey(o);
            }
            if(this.containsKey(key)){
                this.suspendEvents();
                this.removeKey(key);
                this.resumeEvents();
            }
            if(index >= this.length){
                return this.add(key, o);
            }
            this.length++;
            this.items.splice(index, 0, o);
            if(typeof key != 'undefined' && key !== null){
                this.map[key] = o;
            }
            this.keys.splice(index, 0, key);
            this.fireEvent('add', index, o, key);
            return o;
        },

        /**
         * Remove an item from the collection.
         * @param {Object} o The item to remove.
         * @return {Object} The item removed or false if no item was removed.
         */
        remove : function(o){
            return this.removeAt(this.indexOf(o));
        },

        /**
         * Remove an item from a specified index in the collection. Fires the {@link #remove} event when complete.
         * @param {Number} index The index within the collection of the item to remove.
         * @return {Object} The item removed or false if no item was removed.
         */
        removeAt : function(index){
            if(index < this.length && index >= 0){
                this.length--;
                var o = this.items[index];
                this.items.splice(index, 1);
                var key = this.keys[index];
                if(typeof key != 'undefined'){
                    delete this.map[key];
                }
                this.keys.splice(index, 1);
                this.fireEvent('remove', o, key);
                return o;
            }
            return false;
        },

        /**
         * Removed an item associated with the passed key fom the collection.
         * @param {String} key The key of the item to remove.
         * @return {Object} The item removed or false if no item was removed.
         */
        removeKey : function(key){
            return this.removeAt(this.indexOfKey(key));
        },

        /**
         * Returns the number of items in the collection.
         * @return {Number} the number of items in the collection.
         */
        getCount : function(){
            return this.length;
        },

        /**
         * Returns index within the collection of the passed Object.
         * @param {Object} o The item to find the index of.
         * @return {Number} index of the item. Returns -1 if not found.
         */
        indexOf : function(o){
            return this.items.indexOf(o);
        },

        /**
         * Returns index within the collection of the passed key.
         * @param {String} key The key to find the index of.
         * @return {Number} index of the key.
         */
        indexOfKey : function(key){
            return this.keys.indexOf(key);
        },

        /**
         * Returns the item associated with the passed key OR index.
         * Key has priority over index.  This is the equivalent
         * of calling {@link #key} first, then if nothing matched calling {@link #itemAt}.
         * @param {String/Number} key The key or index of the item.
         * @return {Object} If the item is found, returns the item.  If the item was not found, returns <tt>undefined</tt>.
         * If an item was found, but is a Class, returns <tt>null</tt>.
         */
        item : function(key){
            var mk = this.map[key],
                item = mk !== undefined ? mk : (typeof key == 'number') ? this.items[key] : undefined;
            return typeof item != 'function' || this.allowFunctions ? item : null; // for prototype!
        },

        /**
         * Returns the item at the specified index.
         * @param {Number} index The index of the item.
         * @return {Object} The item at the specified index.
         */
        itemAt : function(index){
            return this.items[index];
        },

        /**
         * Returns the item associated with the passed key.
         * @param {String/Number} key The key of the item.
         * @return {Object} The item associated with the passed key.
         */
        key : function(key){
            return this.map[key];
        },

        /**
         * Returns true if the collection contains the passed Object as an item.
         * @param {Object} o  The Object to look for in the collection.
         * @return {Boolean} True if the collection contains the Object as an item.
         */
        contains : function(o){
            return this.indexOf(o) != -1;
        },

        /**
         * Returns true if the collection contains the passed Object as a key.
         * @param {String} key The key to look for in the collection.
         * @return {Boolean} True if the collection contains the Object as a key.
         */
        containsKey : function(key){
            return typeof this.map[key] != 'undefined';
        },

        /**
         * Removes all items from the collection.  Fires the {@link #clear} event when complete.
         */
        clear : function(){
            this.length = 0;
            this.items = [];
            this.keys = [];
            this.map = {};
            this.fireEvent('clear');
        },

        /**
         * Returns the first item in the collection.
         * @return {Object} the first item in the collection..
         */
        first : function(){
            return this.items[0];
        },

        /**
         * Returns the last item in the collection.
         * @return {Object} the last item in the collection..
         */
        last : function(){
            return this.items[this.length-1];
        },

        /**
         * @private
         * Performs the actual sorting based on a direction and a sorting function. Internally,
         * this creates a temporary array of all items in the MixedCollection, sorts it and then writes
         * the sorted array data back into this.items and this.keys
         * @param {String} property Property to sort by ('key', 'value', or 'index')
         * @param {String} dir (optional) Direction to sort 'ASC' or 'DESC'. Defaults to 'ASC'.
         * @param {Function} fn (optional) Comparison function that defines the sort order.
         * Defaults to sorting by numeric value.
         */
        _sort : function(property, dir, fn){
            var i, len,
                dsc   = String(dir).toUpperCase() == 'DESC' ? -1 : 1,

                //this is a temporary array used to apply the sorting function
                c     = [],
                keys  = this.keys,
                items = this.items;

            //default to a simple sorter function if one is not provided
            fn = fn || function(a, b) {
                return a - b;
            };

            //copy all the items into a temporary array, which we will sort
            for(i = 0, len = items.length; i < len; i++){
                c[c.length] = {
                    key  : keys[i],
                    value: items[i],
                    index: i
                };
            }

            //sort the temporary array
            c.sort(function(a, b){
                var v = fn(a[property], b[property]) * dsc;
                if(v === 0){
                    v = (a.index < b.index ? -1 : 1);
                }
                return v;
            });

            //copy the temporary array back into the main this.items and this.keys objects
            for(i = 0, len = c.length; i < len; i++){
                items[i] = c[i].value;
                keys[i]  = c[i].key;
            }

            this.fireEvent('sort', this);
        },

        /**
         * Sorts this collection by <b>item</b> value with the passed comparison function.
         * @param {String} direction (optional) 'ASC' or 'DESC'. Defaults to 'ASC'.
         * @param {Function} fn (optional) Comparison function that defines the sort order.
         * Defaults to sorting by numeric value.
         */
        sort : function(dir, fn){
            this._sort('value', dir, fn);
        },

        /**
         * Reorders each of the items based on a mapping from old index to new index. Internally this
         * just translates into a sort. The 'sort' event is fired whenever reordering has occured.
         * @param {Object} mapping Mapping from old item index to new item index
         */
        reorder: function(mapping) {
            this.suspendEvents();

            var items = this.items,
                index = 0,
                length = items.length,
                order = [],
                remaining = [],
                oldIndex;

            //object of {oldPosition: newPosition} reversed to {newPosition: oldPosition}
            for (oldIndex in mapping) {
                order[mapping[oldIndex]] = items[oldIndex];
            }

            for (index = 0; index < length; index++) {
                if (mapping[index] == undefined) {
                    remaining.push(items[index]);
                }
            }

            for (index = 0; index < length; index++) {
                if (order[index] == undefined) {
                    order[index] = remaining.shift();
                }
            }

            this.clear();
            this.addAll(order);

            this.resumeEvents();
            this.fireEvent('sort', this);
        },

        /**
         * Sorts this collection by <b>key</b>s.
         * @param {String} direction (optional) 'ASC' or 'DESC'. Defaults to 'ASC'.
         * @param {Function} fn (optional) Comparison function that defines the sort order.
         * Defaults to sorting by case insensitive string.
         */
        keySort : function(dir, fn){
            this._sort('key', dir, fn || function(a, b){
                var v1 = String(a).toUpperCase(), v2 = String(b).toUpperCase();
                return v1 > v2 ? 1 : (v1 < v2 ? -1 : 0);
            });
        },

        /**
         * Returns a range of items in this collection
         * @param {Number} startIndex (optional) The starting index. Defaults to 0.
         * @param {Number} endIndex (optional) The ending index. Defaults to the last item.
         * @return {Array} An array of items
         */
        getRange : function(start, end){
            var items = this.items;
            if(items.length < 1){
                return [];
            }
            start = start || 0;
            end = Math.min(typeof end == 'undefined' ? this.length-1 : end, this.length-1);
            var i, r = [];
            if(start <= end){
                for(i = start; i <= end; i++) {
                    r[r.length] = items[i];
                }
            }else{
                for(i = start; i >= end; i--) {
                    r[r.length] = items[i];
                }
            }
            return r;
        },

        /**
         * Filter the <i>objects</i> in this collection by a specific property.
         * Returns a new collection that has been filtered.
         * @param {String} property A property on your objects
         * @param {String/RegExp} value Either string that the property values
         * should start with or a RegExp to test against the property
         * @param {Boolean} anyMatch (optional) True to match any part of the string, not just the beginning
         * @param {Boolean} caseSensitive (optional) True for case sensitive comparison (defaults to False).
         * @return {MixedCollection} The new filtered collection
         */
        filter : function(property, value, anyMatch, caseSensitive){
            if(Ext.isEmpty(value, false)){
                return this.clone();
            }
            value = this.createValueMatcher(value, anyMatch, caseSensitive);
            return this.filterBy(function(o){
                return o && value.test(o[property]);
            });
        },

        /**
         * Filter by a function. Returns a <i>new</i> collection that has been filtered.
         * The passed function will be called with each object in the collection.
         * If the function returns true, the value is included otherwise it is filtered.
         * @param {Function} fn The function to be called, it will receive the args o (the object), k (the key)
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the function is executed. Defaults to this MixedCollection.
         * @return {MixedCollection} The new filtered collection
         */
        filterBy : function(fn, scope){
            var r = new Ext.util.MixedCollection();
            r.getKey = this.getKey;
            var k = this.keys, it = this.items;
            for(var i = 0, len = it.length; i < len; i++){
                if(fn.call(scope||this, it[i], k[i])){
                    r.add(k[i], it[i]);
                }
            }
            return r;
        },

        /**
         * Finds the index of the first matching object in this collection by a specific property/value.
         * @param {String} property The name of a property on your objects.
         * @param {String/RegExp} value A string that the property values
         * should start with or a RegExp to test against the property.
         * @param {Number} start (optional) The index to start searching at (defaults to 0).
         * @param {Boolean} anyMatch (optional) True to match any part of the string, not just the beginning.
         * @param {Boolean} caseSensitive (optional) True for case sensitive comparison.
         * @return {Number} The matched index or -1
         */
        findIndex : function(property, value, start, anyMatch, caseSensitive){
            if(Ext.isEmpty(value, false)){
                return -1;
            }
            value = this.createValueMatcher(value, anyMatch, caseSensitive);
            return this.findIndexBy(function(o){
                return o && value.test(o[property]);
            }, null, start);
        },

        /**
         * Find the index of the first matching object in this collection by a function.
         * If the function returns <i>true</i> it is considered a match.
         * @param {Function} fn The function to be called, it will receive the args o (the object), k (the key).
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the function is executed. Defaults to this MixedCollection.
         * @param {Number} start (optional) The index to start searching at (defaults to 0).
         * @return {Number} The matched index or -1
         */
        findIndexBy : function(fn, scope, start){
            var k = this.keys, it = this.items;
            for(var i = (start||0), len = it.length; i < len; i++){
                if(fn.call(scope||this, it[i], k[i])){
                    return i;
                }
            }
            return -1;
        },

        /**
         * Returns a regular expression based on the given value and matching options. This is used internally for finding and filtering,
         * and by Ext.data.Store#filter
         * @private
         * @param {String} value The value to create the regex for. This is escaped using Ext.escapeRe
         * @param {Boolean} anyMatch True to allow any match - no regex start/end line anchors will be added. Defaults to false
         * @param {Boolean} caseSensitive True to make the regex case sensitive (adds 'i' switch to regex). Defaults to false.
         * @param {Boolean} exactMatch True to force exact match (^ and $ characters added to the regex). Defaults to false. Ignored if anyMatch is true.
         */
        createValueMatcher : function(value, anyMatch, caseSensitive, exactMatch) {
            if (!value.exec) { // not a regex
                var er = Ext.escapeRe;
                value = String(value);

                if (anyMatch === true) {
                    value = er(value);
                } else {
                    value = '^' + er(value);
                    if (exactMatch === true) {
                        value += '$';
                    }
                }
                value = new RegExp(value, caseSensitive ? '' : 'i');
             }
             return value;
        },

        /**
         * Creates a shallow copy of this collection
         * @return {MixedCollection}
         */
        clone : function(){
            var r = new Ext.util.MixedCollection();
            var k = this.keys, it = this.items;
            for(var i = 0, len = it.length; i < len; i++){
                r.add(k[i], it[i]);
            }
            r.getKey = this.getKey;
            return r;
        }
    });
    /**
     * This method calls {@link #item item()}.
     * Returns the item associated with the passed key OR index. Key has priority
     * over index.  This is the equivalent of calling {@link #key} first, then if
     * nothing matched calling {@link #itemAt}.
     * @param {String/Number} key The key or index of the item.
     * @return {Object} If the item is found, returns the item.  If the item was
     * not found, returns <tt>undefined</tt>. If an item was found, but is a Class,
     * returns <tt>null</tt>.
     */
    Ext.util.MixedCollection.prototype.get = Ext.util.MixedCollection.prototype.item;