事件监听通用函数

const 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;
        }
    },
    rmoveHandler: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;
        }
    },
    stopPropagation:function (event) {
        if(event.stopPropagation){
            event.stopPropagation();
        }else{
            event.cancelBubble = true;
        }
    },
    getRelateTarget:function (event) {
        if(event.relatedTarget){
            return event.relatedTarget;
        }else if(event.toElement){
            return event.toElement;
        }else if(event.fromElement){
            return event.fromElement;
        }else {
            return null;
        }
    },
    getButton:function (event) {
        if(document.implementation.hasFeature("MouseEvent","2.0")){
            return event.button;
        }else {
            switch (event.button){
                case 0:
                case 1:
                case 3:
                case 5:
                case 7:
                    return 0;
                case 2:
                case 6:
                    return 2;
                case 4:
                    return 1;
            }
        }
    },
    getCharCode:function (event) {
        if(typeof event.charCode === 'number'){
            return event.charCode;
        }else {
            return event.keyCode;
        }
    }
};