js DOM事件监听与解除的兼容性写法

    function addEvent(obj, type, fn) {
        if (window.addEventListener) {//ie9+ chrome fireFox
            obj.addEventListener(type, fn, false);
        } else if (window.attachEvent) {//旧版本ie(edge不支持)
            obj.attachEvent('on' + type, fn);
        } else {
            obj['on' + type] = fn;
        }
    }

    function removeEvent(obj, type, fn) {
        if (window.removeEventListener) {//ie9+ chrome fireFox
            obj.removeEventListener(type, fn, false);
        } else if (window.detachEvent) {//旧版本ie(edge不支持)
            obj.detachEvent('on' + type, fn);
        } else {
            obj['on' + type] = null;
        }
    }