event.js

这是YUI的源码及相关示例。里面有很多很炫的Javascript效果。

            /**
             * Executes the supplied callback when the item with the supplied
             * id is found.  This is meant to be used to execute behavior as
             * soon as possible as the page loads.  If you use this after the
             * initial page load it will poll for a fixed time for the element.
             * The number of times it will poll and the frequency are
             * configurable.  By default it will poll for 10 seconds.
             *
             * <p>The callback is executed with a single parameter:
             * the custom object parameter, if provided.</p>
             *
             * @method onAvailable
             *
             * @param {string||string[]}   p_id the id of the element, or an array
             * of ids to look for.
             * @param {function} p_fn what to execute when the element is found.
             * @param {object}   p_obj an optional object to be passed back as
             *                   a parameter to p_fn.
             * @param {boolean|object}  p_override If set to true, p_fn will execute
             *                   in the scope of p_obj, if set to an object it
             *                   will execute in the scope of that object
             * @param checkContent {boolean} check child node readiness (onContentReady)
             * @static
             */
            onAvailable: function(p_id, p_fn, p_obj, p_override, checkContent) {

                var a = (YAHOO.lang.isString(p_id)) ? [p_id] : p_id;

                for (var i=0; i<a.length; i=i+1) {
                    onAvailStack.push({id:         a[i], 
                                       fn:         p_fn, 
                                       obj:        p_obj, 
                                       override:   p_override, 
                                       checkReady: checkContent });
                }

                retryCount = this.POLL_RETRYS;

                this.startInterval();
            },

            /**
             * Works the same way as onAvailable, but additionally checks the
             * state of sibling elements to determine if the content of the
             * available element is safe to modify.
             *
             * <p>The callback is executed with a single parameter:
             * the custom object parameter, if provided.</p>
             *
             * @method onContentReady
             *
             * @param {string}   p_id the id of the element to look for.
             * @param {function} p_fn what to execute when the element is ready.
             * @param {object}   p_obj an optional object to be passed back as
             *                   a parameter to p_fn.
             * @param {boolean|object}  p_override If set to true, p_fn will execute
             *                   in the scope of p_obj.  If an object, p_fn will
             *                   exectute in the scope of that object
             *
             * @static
             */
            onContentReady: function(p_id, p_fn, p_obj, p_override) {
                this.onAvailable(p_id, p_fn, p_obj, p_override, true);
            },

            /**
             * Executes the supplied callback when the DOM is first usable.  This
             * will execute immediately if called after the DOMReady event has
             * fired.   @todo the DOMContentReady event does not fire when the
             * script is dynamically injected into the page.  This means the
             * DOMReady custom event will never fire in FireFox or Opera when the
             * library is injected.  It _will_ fire in Safari, and the IE 
             * implementation would allow for us to fire it if the defered script
             * is not available.  We want this to behave the same in all browsers.
             * Is there a way to identify when the script has been injected 
             * instead of included inline?  Is there a way to know whether the 
             * window onload event has fired without having had a listener attached 
             * to it when it did so?
             *
             * <p>The callback is a CustomEvent, so the signature is:</p>
             * <p>type &lt;string&gt;, args &lt;array&gt;, customobject &lt;object&gt;</p>
             * <p>For DOMReady events, there are no fire argments, so the
             * signature is:</p>
             * <p>"DOMReady", [], obj</p>
             *
             *
             * @method onDOMReady
             *
             * @param {function} p_fn what to execute when the element is found.
             * @param {object}   p_obj an optional object to be passed back as
             *                   a parameter to p_fn.
             * @param {boolean|object}  p_scope If set to true, p_fn will execute
             *                   in the scope of p_obj, if set to an object it
             *                   will execute in the scope of that object
             *
             * @static
             */
            onDOMReady: function(p_fn, p_obj, p_override) {
                if (this.DOMReady) {
                    setTimeout(function() {
                        var s = window;
                        if (p_override) {
                            if (p_override === true) {
                                s = p_obj;
                            } else {
                                s = p_override;
                            }
                        }
                        p_fn.call(s, "DOMReady", [], p_obj);
                    }, 0);
                } else {
                    this.DOMReadyEvent.subscribe(p_fn, p_obj, p_override);
                }
            },


            /**
             * Appends an event handler
             *
             * @method _addListener
             *
             * @param {String|HTMLElement|Array|NodeList} el An id, an element 
             *  reference, or a collection of ids and/or elements to assign the 
             *  listener to.
             * @param {String}   sType     The type of event to append
             * @param {Function} fn        The method the event invokes
             * @param {Object}   obj    An arbitrary object that will be 
             *                             passed as a parameter to the handler
             * @param {Boolean|object}  override  If true, the obj passed in becomes
             *                             the execution scope of the listener. If an
             *                             object, this object becomes the execution
             *                             scope.
             * @param {boolen}      capture capture or bubble phase
             * @return {Boolean} True if the action was successful or defered,
             *                        false if one or more of the elements 
             *                        could not have the listener attached,
             *                        or if the operation throws an exception.
             * @private
             * @static
             */
            _addListener: function(el, sType, fn, obj, override, capture) {

                if (!fn || !fn.call) {
                    return false;
                }

                // The el argument can be an array of elements or element ids.
                if ( this._isValidCollection(el)) {
                    var ok = true;
                    for (var i=0,len=el.length; i<len; ++i) {
                        ok = this._addListener(el[i], 
                                       sType, 
                                       fn, 
                                       obj, 
                                       override, 
                                       capture) && ok;
                    }
                    return ok;

                } else if (YAHOO.lang.isString(el)) {
                    var oEl = this.getEl(el);
                    // If the el argument is a string, we assume it is 
                    // actually the id of the element.  If the page is loaded
                    // we convert el to the actual element, otherwise we 
                    // defer attaching the event until onload event fires

                    // check to see if we need to delay hooking up the event 
                    // until after the page loads.
                    if (oEl) {
                        el = oEl;
                    } else {
                        // defer adding the event until the element is available
                        this.onAvailable(el, function() {
                           YAHOO.util.Event._addListener(el, sType, fn, obj, override, capture);
                        });

                        return true;
                    }
                }

                // Element should be an html element or an array if we get 
                // here.
                if (!el) {
                    return false;
                }

                // we need to make sure we fire registered unload events 
                // prior to automatically unhooking them.  So we hang on to 
                // these instead of attaching them to the window and fire the
                // handles explicitly during our one unload event.
                if ("unload" == sType && obj !== this) {
                    unloadListeners[unloadListeners.length] =
                            [el, sType, fn, obj, override, capture];
                    return true;
                }


                // if the user chooses to override the scope, we use the custom
                // object passed in, otherwise the executing scope will be the
                // HTML element that the event is registered on
                var scope = el;
                if (override) {
                    if (override === true) {
                        scope = obj;
                    } else {
                        scope = override;
                    }
                }

                // wrap the function so we can return the obj object when
                // the event fires;
                var wrappedFn = function(e) {
                        return fn.call(scope, YAHOO.util.Event.getEvent(e, el), 
                                obj);
                    };

                var li = [el, sType, fn, wrappedFn, scope, obj, override, capture];
                var index = listeners.length;
                // cache the listener so we can try to automatically unload
                listeners[index] = li;

                if (this.useLegacyEvent(el, sType)) {
                    var legacyIndex = this.getLegacyIndex(el, sType);

                    // Add a new dom0 wrapper if one is not detected for this
                    // element
                    if ( legacyIndex == -1 || 
                                el != legacyEvents[legacyIndex][0] ) {

                        legacyIndex = legacyEvents.length;
                        legacyMap[el.id + sType] = legacyIndex;

                        // cache the signature for the DOM0 event, and 
                        // include the existing handler for the event, if any
                        legacyEvents[legacyIndex] = 
                            [el, sType, el["on" + sType]];
                        legacyHandlers[legacyIndex] = [];

                        el["on" + sType] = 
                            function(e) {
                                YAHOO.util.Event.fireLegacyEvent(
                                    YAHOO.util.Event.getEvent(e), legacyIndex);
                            };
                    }

                    // add a reference to the wrapped listener to our custom
                    // stack of events
                    //legacyHandlers[legacyIndex].push(index);
                    legacyHandlers[legacyIndex].push(li);

                } else {
                    try {
                        this._simpleAdd(el, sType, wrappedFn, capture);
                    } catch(ex) {
                        // handle an error trying to attach an event.  If it fails
                        // we need to clean up the cache
                        this.lastError = ex;
                        this._removeListener(el, sType, fn, capture);
                        return false;
                    }
                }

                return true;
                
            },


            /**
             * Appends an event handler
             *
             * @method addListener
             *
             * @param {String|HTMLElement|Array|NodeList} el An id, an element 
             *  reference, or a collection of ids and/or elements to assign the 
             *  listener to.
             * @param {String}   sType     The type of event to append
             * @param {Function} fn        The method the event invokes
             * @param {Object}   obj    An arbitrary object that will be 
             *                             passed as a parameter to the handler
             * @param {Boolean|object}  override  If true, the obj passed in becomes
             *                             the execution scope of the listener. If an
             *                             object, this object becomes the execution
             *                             scope.
             * @return {Boolean} True if the action was successful or defered,
             *                        false if one or more of the elements 
             *                        could not have the listener attached,
             *                        or if the operation throws an exception.
             * @static
             */
            addListener: function (el, sType, fn, obj, override) {
                return this._addListener(el, sType, fn, obj, override, false);
            },

            /**
             * Appends a focus event handler.  (The focusin event is used for Internet Explorer, 
             * the focus, capture-event for Opera, WebKit, and Gecko.)
             *
             * @method addFocusListener
             *
             * @param {String|HTMLElement|Array|NodeList} el An id, an element 
             *  reference, or a collection of ids and/or elements to assign the 
             *  listener to.
             * @param {Function} fn        The method the event invokes
             * @param {Object}   obj    An arbitrary object that will be 
             *                             passed as a parameter to the handler
             * @param {Boolean|object}  override  If true, the obj passed in becomes
             *                             the execution scope of the listener. If an
             *                             object, this object becomes the execution
             *                             scope.
             * @return {Boolean} True if the action was successful or defered,
             *                        false if one or more of the elements 
             *                        could not have the listener attached,
             *                        or if the operation throws an exception.
             * @static
             */
            addFocusListener: function (el, fn, obj, override) {
                return this._addListener(el, _FOCUS, fn, obj, override, true);
            },          


            /**
             * Removes a focus event listener
             *
             * @method removeFocusListener
             *
             * @param {String|HTMLElement|Array|NodeList} el An id, an element 
             *  reference, or a collection of ids and/or elements to remove
             *  the listener from.
             * @param {Function} fn the method the event invokes.  If fn is
             *  undefined, then all event handlers for the type of event are 
             *  removed.
             * @return {boolean} true if the unbind was successful, false 
             *  otherwise.
             * @static
             */
            removeFocusListener: function (el, fn) { 
                return this._removeListener(el, _FOCUS, fn, true);
            },

            /**
             * Appends a blur event handler.  (The focusout event is used for Internet Explorer, 
             * the focusout, capture-event for Opera, WebKit, and Gecko.)
             *
             * @method addBlurListener
             *
             * @param {String|HTMLElement|Array|NodeList} el An id, an element 
             *  reference, or a collection of ids and/or elements to assign the 
             *  listener to.
             * @param {Function} fn        The method the event invokes
             * @param {Object}   obj    An arbitrary object that will be 
             *                             passed as a parameter to the handler
             * @param {Boolean|object}  override  If true, the obj passed in becomes
             *                             the execution scope of the listener. If an
             *                             object, this object becomes the execution
             *                             scope.
             * @return {Boolean} True if the action was successful or defered,
             *                        false if one or more of the elements 
             *                        could not have the listener attached,
             *                        or if the operation throws an exception.
             * @static
             */
            addBlurListener: function (el, fn, obj, override) {
                return this._addListener(el, _BLUR, fn, obj, override, true);
            },