事件处理程序EventUtil

/**********事件处理程序**********
*EventUtil.js
*浏览器兼容，《高三》13章 P354
*2014-12-8
********************************/
var EventUtil = {
    addHandler: 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;
        }
    },
    removeHandler: 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;
        }
    },

    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;
        }
    },

    /********由于IE不支持事件捕获，因此这个方法只适用于事件冒泡阶段*********/
    stopPropagation: function (event) {
        if (event.stopPropagation) {
            event.stopPropagation();
        }
        else {
            event.cancelBubble = true;
        }
    },

    /*****按键时触发，返回按键所代表字符的ASCII码******/
    getCharCode: function (event) {
        if (typeof event.charCode == "number") {
            return event.charCode;
        }
        else {
            return event.keyCode; //IE8之前、Opera
        }
    }
}