    /**
     * @class Ext.Function
     *
     * A collection of useful static methods to deal with function callbacks
     * @singleton
     * @alternateClassName Ext.util.Functions
     */
    Ext.Function = {

        /**
         * A very commonly used method throughout the framework. It acts as a wrapper around another method
         * which originally accepts 2 arguments for `name` and `value`.
         * The wrapped function then allows "flexible" value setting of either:
         *
         * - `name` and `value` as 2 arguments
         * - one single object argument with multiple key - value pairs
         *
         * For example:
         *
         *     var setValue = Ext.Function.flexSetter(function(name, value) {
         *         this[name] = value;
         *     });
         *
         *     // Afterwards
         *     // Setting a single name - value
         *     setValue('name1', 'value1');
         *
         *     // Settings multiple name - value pairs
         *     setValue({
         *         name1: 'value1',
         *         name2: 'value2',
         *         name3: 'value3'
         *     });
         *
         * @param {Function} setter
         * @returns {Function} flexSetter
         */
        flexSetter: function(fn) {
            return function(a, b) {
                var k, i;

                if (a === null) {
                    return this;
                }

                if (typeof a !== 'string') {
                    for (k in a) {
                        if (a.hasOwnProperty(k)) {
                            fn.call(this, k, a[k]);
                        }
                    }

                    if (Ext.enumerables) {
                        for (i = Ext.enumerables.length; i--;) {
                            k = Ext.enumerables[i];
                            if (a.hasOwnProperty(k)) {
                                fn.call(this, k, a[k]);
                            }
                        }
                    }
                } else {
                    fn.call(this, a, b);
                }

                return this;
            };
        },

        /**
         * Create a new function from the provided `fn`, change `this` to the provided scope, optionally
         * overrides arguments for the call. (Defaults to the arguments passed by the caller)
         *
         * {@link Ext#bind Ext.bind} is alias for {@link Ext.Function#bind Ext.Function.bind}
         *
         * @param {Function} fn The function to delegate.
         * @param {Object} scope (optional) The scope (`this` reference) in which the function is executed.
         * **If omitted, defaults to the browser window.**
         * @param {Array} args (optional) Overrides arguments for the call. (Defaults to the arguments passed by the caller)
         * @param {Boolean/Number} appendArgs (optional) if True args are appended to call args instead of overriding,
         * if a number the args are inserted at the specified position
         * @return {Function} The new function
         */
        bind: function(fn, scope, args, appendArgs) {
            if (arguments.length === 2) {
                return function() {
                    return fn.apply(scope, arguments);
                }
            }

            var method = fn,
                slice = Array.prototype.slice;

            return function() {
                var callArgs = args || arguments;

                if (appendArgs === true) {
                    callArgs = slice.call(arguments, 0);
                    callArgs = callArgs.concat(args);
                }
                else if (typeof appendArgs == 'number') {
                    callArgs = slice.call(arguments, 0); // copy arguments first
                    Ext.Array.insert(callArgs, appendArgs, args);
                }

                return method.apply(scope || window, callArgs);
            };
        },

        /**
         * Create a new function from the provided `fn`, the arguments of which are pre-set to `args`.
         * New arguments passed to the newly created callback when it's invoked are appended after the pre-set ones.
         * This is especially useful when creating callbacks.
         *
         * For example:
         *
         *     var originalFunction = function(){
         *         alert(Ext.Array.from(arguments).join(' '));
         *     };
         *
         *     var callback = Ext.Function.pass(originalFunction, ['Hello', 'World']);
         *
         *     callback(); // alerts 'Hello World'
         *     callback('by Me'); // alerts 'Hello World by Me'
         *
         * {@link Ext#pass Ext.pass} is alias for {@link Ext.Function#pass Ext.Function.pass}
         *
         * @param {Function} fn The original function
         * @param {Array} args The arguments to pass to new callback
         * @param {Object} scope (optional) The scope (`this` reference) in which the function is executed.
         * @return {Function} The new callback function
         */
        pass: function(fn, args, scope) {
            if (!Ext.isArray(args)) {
                args = Ext.Array.clone(args);
            }

            return function() {
                args.push.apply(args, arguments);
                return fn.apply(scope || this, args);
            };
        },

        /**
         * Create an alias to the provided method property with name `methodName` of `object`.
         * Note that the execution scope will still be bound to the provided `object` itself.
         *
         * @param {Object/Function} object
         * @param {String} methodName
         * @return {Function} aliasFn
         */
        alias: function(object, methodName) {
            return function() {
                return object[methodName].apply(object, arguments);
            };
        },

        /**
         * Create a "clone" of the provided method. The returned method will call the given
         * method passing along all arguments and the "this" pointer and return its result.
         *
         * @param {Function} method
         * @return {Function} cloneFn
         */
        clone: function(method) {
            return function() {
                return method.apply(this, arguments);
            };
        },

        /**
         * Creates an interceptor function. The passed function is called before the original one. If it returns false,
         * the original one is not called. The resulting function returns the results of the original function.
         * The passed function is called with the parameters of the original function. Example usage:
         *
         *     var sayHi = function(name){
         *         alert('Hi, ' + name);
         *     }
         *
         *     sayHi('Fred'); // alerts "Hi, Fred"
         *
         *     // create a new function that validates input without
         *     // directly modifying the original function:
         *     var sayHiToFriend = Ext.Function.createInterceptor(sayHi, function(name){
         *         return name == 'Brian';
         *     });
         *
         *     sayHiToFriend('Fred');  // no alert
         *     sayHiToFriend('Brian'); // alerts "Hi, Brian"
         *
         * @param {Function} origFn The original function.
         * @param {Function} newFn The function to call before the original
         * @param {Object} scope (optional) The scope (`this` reference) in which the passed function is executed.
         * **If omitted, defaults to the scope in which the original function is called or the browser window.**
         * @param {Object} returnValue (optional) The value to return if the passed function return false (defaults to null).
         * @return {Function} The new function
         */
        createInterceptor: function(origFn, newFn, scope, returnValue) {
            var method = origFn;
            if (!Ext.isFunction(newFn)) {
                return origFn;
            }
            else {
                return function() {
                    var me = this,
                        args = arguments;
                    newFn.target = me;
                    newFn.method = origFn;
                    return (newFn.apply(scope || me || window, args) !== false) ? origFn.apply(me || window, args) : returnValue || null;
                };
            }
        },

        /**
         * Creates a delegate (callback) which, when called, executes after a specific delay.
         *
         * @param {Function} fn The function which will be called on a delay when the returned function is called.
         * Optionally, a replacement (or additional) argument list may be specified.
         * @param {Number} delay The number of milliseconds to defer execution by whenever called.
         * @param {Object} scope (optional) The scope (`this` reference) used by the function at execution time.
         * @param {Array} args (optional) Override arguments for the call. (Defaults to the arguments passed by the caller)
         * @param {Boolean/Number} appendArgs (optional) if True args are appended to call args instead of overriding,
         * if a number the args are inserted at the specified position.
         * @return {Function} A function which, when called, executes the original function after the specified delay.
         */
        createDelayed: function(fn, delay, scope, args, appendArgs) {
            if (scope || args) {
                fn = Ext.Function.bind(fn, scope, args, appendArgs);
            }

            return function() {
                var me = this,
                    args = Array.prototype.slice.call(arguments);

                setTimeout(function() {
                    fn.apply(me, args);
                }, delay);
            }
        },

        /**
         * Calls this function after the number of millseconds specified, optionally in a specific scope. Example usage:
         *
         *     var sayHi = function(name){
         *         alert('Hi, ' + name);
         *     }
         *
         *     // executes immediately:
         *     sayHi('Fred');
         *
         *     // executes after 2 seconds:
         *     Ext.Function.defer(sayHi, 2000, this, ['Fred']);
         *
         *     // this syntax is sometimes useful for deferring
         *     // execution of an anonymous function:
         *     Ext.Function.defer(function(){
         *         alert('Anonymous');
         *     }, 100);
         *
         * {@link Ext#defer Ext.defer} is alias for {@link Ext.Function#defer Ext.Function.defer}
         *
         * @param {Function} fn The function to defer.
         * @param {Number} millis The number of milliseconds for the setTimeout call
         * (if less than or equal to 0 the function is executed immediately)
         * @param {Object} scope (optional) The scope (`this` reference) in which the function is executed.
         * **If omitted, defaults to the browser window.**
         * @param {Array} args (optional) Overrides arguments for the call. (Defaults to the arguments passed by the caller)
         * @param {Boolean/Number} appendArgs (optional) if True args are appended to call args instead of overriding,
         * if a number the args are inserted at the specified position
         * @return {Number} The timeout id that can be used with clearTimeout
         */
        defer: function(fn, millis, scope, args, appendArgs) {
            fn = Ext.Function.bind(fn, scope, args, appendArgs);
            if (millis > 0) {
                return setTimeout(fn, millis);
            }
            fn();
            return 0;
        },

        /**
         * Create a combined function call sequence of the original function + the passed function.
         * The resulting function returns the results of the original function.
         * The passed function is called with the parameters of the original function. Example usage:
         *
         *     var sayHi = function(name){
         *         alert('Hi, ' + name);
         *     }
         *
         *     sayHi('Fred'); // alerts "Hi, Fred"
         *
         *     var sayGoodbye = Ext.Function.createSequence(sayHi, function(name){
         *         alert('Bye, ' + name);
         *     });
         *
         *     sayGoodbye('Fred'); // both alerts show
         *
         * @param {Function} originalFn The original function.
         * @param {Function} newFn The function to sequence
         * @param {Object} scope (optional) The scope (`this` reference) in which the passed function is executed.
         * If omitted, defaults to the scope in which the original function is called or the browser window.
         * @return {Function} The new function
         */
        createSequence: function(originalFn, newFn, scope) {
            if (!newFn) {
                return originalFn;
            }
            else {
                return function() {
                    var result = originalFn.apply(this, arguments);
                    newFn.apply(scope || this, arguments);
                    return result;
                };
            }
        },

        /**
         * Creates a delegate function, optionally with a bound scope which, when called, buffers
         * the execution of the passed function for the configured number of milliseconds.
         * If called again within that period, the impending invocation will be canceled, and the
         * timeout period will begin again.
         *
         * @param {Function} fn The function to invoke on a buffered timer.
         * @param {Number} buffer The number of milliseconds by which to buffer the invocation of the
         * function.
         * @param {Object} scope (optional) The scope (`this` reference) in which
         * the passed function is executed. If omitted, defaults to the scope specified by the caller.
         * @param {Array} args (optional) Override arguments for the call. Defaults to the arguments
         * passed by the caller.
         * @return {Function} A function which invokes the passed function after buffering for the specified time.
         */
        createBuffered: function(fn, buffer, scope, args) {
            var timerId;

            return function() {
                if (!scope) {
                    scope = this;
                }

                if (!args) {
                    args = Array.prototype.slice.call(arguments);
                }

                if (timerId) {
                    clearTimeout(timerId);
                    timerId = null;
                }

                timerId = setTimeout(function(){
                    fn.apply(scope, args);
                }, buffer);
            };
        },

        /**
         * Creates a throttled version of the passed function which, when called repeatedly and
         * rapidly, invokes the passed function only after a certain interval has elapsed since the
         * previous invocation.
         *
         * This is useful for wrapping functions which may be called repeatedly, such as
         * a handler of a mouse move event when the processing is expensive.
         *
         * @param {Function} fn The function to execute at a regular time interval.
         * @param {Number} interval The interval **in milliseconds** on which the passed function is executed.
         * @param {Object} scope (optional) The scope (`this` reference) in which
         * the passed function is executed. If omitted, defaults to the scope specified by the caller.
         * @returns {Function} A function which invokes the passed function at the specified interval.
         */
        createThrottled: function(fn, interval, scope) {
            var lastCallTime, elapsed, lastArgs, timer, execute = function() {
                fn.apply(scope || this, lastArgs);
                lastCallTime = new Date().getTime();
            };

            return function() {
                elapsed = new Date().getTime() - lastCallTime;
                lastArgs = arguments;

                clearTimeout(timer);
                if (!lastCallTime || (elapsed >= interval)) {
                    execute();
                } else {
                    timer = setTimeout(execute, interval - elapsed);
                }
            };
        },

        interceptBefore: function(object, methodName, fn) {
            var method = object[methodName] || Ext.emptyFn;

            return object[methodName] = function() {
                var ret = fn.apply(this, arguments);
                method.apply(this, arguments);

                return ret;
            };
        },

        interceptAfter: function(object, methodName, fn) {
            var method = object[methodName] || Ext.emptyFn;

            return object[methodName] = function() {
                method.apply(this, arguments);
                return fn.apply(this, arguments);
            };
        }
    };

    /**
     * @method
     * @member Ext
     * @alias Ext.Function#defer
     */
    Ext.defer = Ext.Function.alias(Ext.Function, 'defer');

    /**
     * @method
     * @member Ext
     * @alias Ext.Function#pass
     */
    Ext.pass = Ext.Function.alias(Ext.Function, 'pass');

    /**
     * @method
     * @member Ext
     * @alias Ext.Function#bind
     */
    Ext.bind = Ext.Function.alias(Ext.Function, 'bind');