eventShim.js

/* Copyright (c) 2012 Jeremy McPeak http://www.wdonline.com
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

(function() {

    function init() {

        var loadedForBrowser = false;
        
        if (Object.defineProperty) {
            // create an MS event object and get prototype
            var proto = document.createEventObject().constructor.prototype;

            /**
             * Indicates whether an event propagates up from the target.
             * @returns Boolean
             */
            Object.defineProperty(proto, "bubbles", {
                get: function() {
                    // not a complete list of DOM3 events; some of these IE8 doesn't support
                    var bubbleEvents = ["select", "scroll", "click", "dblclick",
                        "mousedown", "mousemove", "mouseout", "mouseover", "mouseup", "wheel", "textinput",
                        "keydown", "keypress", "keyup"],
                        type = this.type;

                    for (var i = 0, l = bubbleEvents.length; i < l; i++) {
                        if (type === bubbleEvents[i]) {
                            return true;
                        }
                    }

                    return false;
                }
            });


            /**
             * Indicates whether or not preventDefault() was called on the event.
             * @returns Boolean
             */
            Object.defineProperty(proto, "defaultPrevented", {
                get: function() {
                    // if preventDefault() was never called, or returnValue not given a value
                    // then returnValue is undefined
                    var returnValue = this.returnValue,
                        undef;

                    return !(returnValue === undef || returnValue);
                }
            });


            /**
             * Gets the secondary targets of mouseover and mouseout events (toElement and fromElement)
             * @returns EventTarget or {null}
             */
            Object.defineProperty(proto, "relatedTarget", {
                get: function() {
                    var type = this.type;

                    if (type === "mouseover" || type === "mouseout") {
                        return (type === "mouseover") ? this.fromElement : this.toElement;
                    }

                    return null;
                }
            });


            /**
             * Gets the target of the event (srcElement)
             * @returns EventTarget
             */
            Object.defineProperty(proto, "target", {
                get: function() { return this.srcElement; }
            });
            
            loadedForBrowser = true;
        }


        if (!proto.preventDefault) {
            /**
             * Cancels the event if it is cancelable. (returnValue)
             * @returns {undefined}
             */
            proto.preventDefault = function() {
                this.returnValue = false;
            };
            
            loadedForBrowser = true;
        }

        if (!proto.stopPropagation) {
            /**
             * Prevents further propagation of the current event. (cancelBubble())
             * @returns {undefined}
             */
            proto.stopPropagation = function() {
                this.cancelBubble = true;
            };
            
            loadedForBrowser = true;
        }

        /***************************************
         *
         * Event Listener Setup
         *    Nothing complex here
         *
         ***************************************/
        if (!Element.prototype.addEventListener) {
            /**
             * Determines if the provided object implements EventListener
             * @returns boolean
            */
            var implementsEventListener = function(obj) {
                return (typeof obj !== "function" && typeof obj["handleEvent"] === "function");
            };

            var customELKey = "__eventShim__";

            /**
             * Adds an event listener to the DOM object
             * @returns {undefined}
             */
            var addEventListenerFunc = function(type, handler, useCapture) {
                // useCapture isn't used; it's IE!

                var fn = handler;

                if (implementsEventListener(handler)) {

                    if (typeof handler[customELKey] !== "function") {
                        handler[customELKey] = function(e) {
                            handler["handleEvent"](e);
                        };
                    }

                    fn = handler[customELKey];
                }

                this.attachEvent("on" + type, fn.bind(this));
            };

            /**
             * Removes an event listener to the DOM object
             * @returns {undefined}
             */
            var removeEventListenerFunc = function(type, handler, useCapture) {
                // useCapture isn't used; it's IE!

                var fn = handler;

                if (implementsEventListener(handler)) {
                    fn = handler[customELKey];
                }

                this.detachEvent("on" + type, fn.bind(this));
            };

            // setup the DOM and window objects
            HTMLDocument.prototype.addEventListener = addEventListenerFunc;
            HTMLDocument.prototype.removeEventListener = removeEventListenerFunc;

            Element.prototype.addEventListener = addEventListenerFunc;
            Element.prototype.removeEventListener = removeEventListenerFunc;

            window.addEventListener = addEventListenerFunc;
            window.removeEventListener = removeEventListenerFunc;
            
            loadedForBrowser = true;
        }

        return {
            loadedForBrowser : loadedForBrowser
        };
    }

    // check for AMD support
    if (typeof define === "function" && define["amd"]) {
        define(init);
    } else {
        return init();
    }

}());