跨浏览器的事件对象

var eventUtil = {
    addEventHandler: function(element, type, handler) {
        if (element.addEventListener) {
            element.addEventListener(type, handler, false);
        } else if (element.attachEvent) {
            element.attachEvent('on' + type, handler);
        } else {
            element['on' + type] = handler;
        }
    },

    getEvent: function(event) {
        return event ? event : window.event;
    },

    getTarget: function(event) {
        return event.target || event.srcElement;
    },

    preventDefault: function(event) {
        if (event.preventDefault) {
            event.preventDefault;
        } else {
            event.returnValue = false;
        }
    },

    stopPropagation: function(event) {
        if (event.stopPropagation) {
            event.stopPropagation;
        } else {
            event.cancelBubble = true;
        }
    },

    removeEventHandler: function(element, type, handler) {
        if (element.removeEventListener) {
            element.removeEventListener(type, handler, false);
        } else if (element.detachEvent) {
            element.detachEvent('on' + type, handler);
        } else {
            element['on' + type] = null;
        }
    }
};

由于 IE 不支持事件捕获，因此以上跨浏览器的事件对象中的 preventDefault() 只能阻止事件冒泡！