event.js

这是YUI的源码及相关示例。里面有很多很炫的Javascript效果。

 * Returns the execution scope for this listener.  If override was set to true
 * the custom obj will be the scope.  If override is an object, that is the
 * scope, otherwise the default scope will be used.
 * @method getScope
 * @param {Object} defaultScope the scope to use if this listener does not
 *                              override it.
 */
YAHOO.util.Subscriber.prototype.getScope = function(defaultScope) {
    if (this.override) {
        if (this.override === true) {
            return this.obj;
        } else {
            return this.override;
        }
    }
    return defaultScope;
};

/**
 * Returns true if the fn and obj match this objects properties.
 * Used by the unsubscribe method to match the right subscriber.
 *
 * @method contains
 * @param {Function} fn the function to execute
 * @param {Object} obj an object to be passed along when the event fires
 * @return {boolean} true if the supplied arguments match this 
 *                   subscriber's signature.
 */
YAHOO.util.Subscriber.prototype.contains = function(fn, obj) {
    if (obj) {
        return (this.fn == fn && this.obj == obj);
    } else {
        return (this.fn == fn);
    }
};

/**
 * @method toString
 */
YAHOO.util.Subscriber.prototype.toString = function() {
    return "Subscriber { obj: " + this.obj  + 
           ", override: " +  (this.override || "no") + " }";
};

/**
 * The Event Utility provides utilities for managing DOM Events and tools
 * for building event systems
 *
 * @module event
 * @title Event Utility
 * @namespace YAHOO.util
 * @requires yahoo
 */

// The first instance of Event will win if it is loaded more than once.
// @TODO this needs to be changed so that only the state data that needs to
// be preserved is kept, while methods are overwritten/added as needed.
// This means that the module pattern can't be used.
if (!YAHOO.util.Event) {

/**
 * The event utility provides functions to add and remove event listeners,
 * event cleansing.  It also tries to automatically remove listeners it
 * registers during the unload event.
 *
 * @class Event
 * @static
 */
    YAHOO.util.Event = function() {

        /**
         * True after the onload event has fired
         * @property loadComplete
         * @type boolean
         * @static
         * @private
         */
        var loadComplete =  false;

        /**
         * Cache of wrapped listeners
         * @property listeners
         * @type array
         * @static
         * @private
         */
        var listeners = [];

        /**
         * User-defined unload function that will be fired before all events
         * are detached
         * @property unloadListeners
         * @type array
         * @static
         * @private
         */
        var unloadListeners = [];

        /**
         * Cache of DOM0 event handlers to work around issues with DOM2 events
         * in Safari
         * @property legacyEvents
         * @static
         * @private
         */
        var legacyEvents = [];

        /**
         * Listener stack for DOM0 events
         * @property legacyHandlers
         * @static
         * @private
         */
        var legacyHandlers = [];

        /**
         * The number of times to poll after window.onload.  This number is
         * increased if additional late-bound handlers are requested after
         * the page load.
         * @property retryCount
         * @static
         * @private
         */
        var retryCount = 0;

        /**
         * onAvailable listeners
         * @property onAvailStack
         * @static
         * @private
         */
        var onAvailStack = [];

        /**
         * Lookup table for legacy events
         * @property legacyMap
         * @static
         * @private
         */
        var legacyMap = [];

        /**
         * Counter for auto id generation
         * @property counter
         * @static
         * @private
         */
        var counter = 0;
        
        /**
         * Normalized keycodes for webkit/safari
         * @property webkitKeymap
         * @type {int: int}
         * @private
         * @static
         * @final
         */
        var webkitKeymap = {
            63232: 38, // up
            63233: 40, // down
            63234: 37, // left
            63235: 39, // right
            63276: 33, // page up
            63277: 34, // page down
            25: 9      // SHIFT-TAB (Safari provides a different key code in
                       // this case, even though the shiftKey modifier is set)
        };
        
        // String constants used by the addFocusListener and removeFocusListener methods
        var _FOCUS = YAHOO.env.ua.ie ? "focusin" : "focus";
        var _BLUR = YAHOO.env.ua.ie ? "focusout" : "blur";      

        return {

            /**
             * The number of times we should look for elements that are not
             * in the DOM at the time the event is requested after the document
             * has been loaded.  The default is 2000@amp;20 ms, so it will poll
             * for 40 seconds or until all outstanding handlers are bound
             * (whichever comes first).
             * @property POLL_RETRYS
             * @type int
             * @static
             * @final
             */
            POLL_RETRYS: 2000,

            /**
             * The poll interval in milliseconds
             * @property POLL_INTERVAL
             * @type int
             * @static
             * @final
             */
            POLL_INTERVAL: 20,

            /**
             * Element to bind, int constant
             * @property EL
             * @type int
             * @static
             * @final
             */
            EL: 0,

            /**
             * Type of event, int constant
             * @property TYPE
             * @type int
             * @static
             * @final
             */
            TYPE: 1,

            /**
             * Function to execute, int constant
             * @property FN
             * @type int
             * @static
             * @final
             */
            FN: 2,

            /**
             * Function wrapped for scope correction and cleanup, int constant
             * @property WFN
             * @type int
             * @static
             * @final
             */
            WFN: 3,

            /**
             * Object passed in by the user that will be returned as a 
             * parameter to the callback, int constant.  Specific to
             * unload listeners
             * @property OBJ
             * @type int
             * @static
             * @final
             */
            UNLOAD_OBJ: 3,

            /**
             * Adjusted scope, either the element we are registering the event
             * on or the custom object passed in by the listener, int constant
             * @property ADJ_SCOPE
             * @type int
             * @static
             * @final
             */
            ADJ_SCOPE: 4,

            /**
             * The original obj passed into addListener
             * @property OBJ
             * @type int
             * @static
             * @final
             */
            OBJ: 5,

            /**
             * The original scope parameter passed into addListener
             * @property OVERRIDE
             * @type int
             * @static
             * @final
             */
            OVERRIDE: 6,

            /**
             * The original capture parameter passed into _addListener
             * @property CAPTURE
             * @type int
             * @static
             * @final
             */
            CAPTURE: 7,


            /**
             * addListener/removeListener can throw errors in unexpected scenarios.
             * These errors are suppressed, the method returns false, and this property
             * is set
             * @property lastError
             * @static
             * @type Error
             */
            lastError: null,

            /**
             * Safari detection
             * @property isSafari
             * @private
             * @static
             * @deprecated use YAHOO.env.ua.webkit
             */
            isSafari: YAHOO.env.ua.webkit,
            
            /**
             * webkit version
             * @property webkit
             * @type string
             * @private
             * @static
             * @deprecated use YAHOO.env.ua.webkit
             */
            webkit: YAHOO.env.ua.webkit,
            
            /**
             * IE detection 
             * @property isIE
             * @private
             * @static
             * @deprecated use YAHOO.env.ua.ie
             */
            isIE: YAHOO.env.ua.ie,

            /**
             * poll handle
             * @property _interval
             * @static
             * @private
             */
            _interval: null,

            /**
             * document readystate poll handle
             * @property _dri
             * @static
             * @private
             */
             _dri: null,

            /**
             * True when the document is initially usable
             * @property DOMReady
             * @type boolean
             * @static
             */
            DOMReady: false,

            /**
             * Errors thrown by subscribers of custom events are caught
             * and the error message is written to the debug console.  If
             * this property is set to true, it will also re-throw the
             * error.
             * @property throwErrors
             * @type boolean
             * @default false
             */
            throwErrors: false,

            /**
             * @method startInterval
             * @static
             * @private
             */
            startInterval: function() {
                if (!this._interval) {
                    var self = this;
                    var callback = function() { self._tryPreloadAttach(); };
                    this._interval = setInterval(callback, this.POLL_INTERVAL);
                }
            },