jquery 浏览器判断

   (function ($) {
            var _a = window.navigator.userAgent.toLowerCase();
            var isIE = _a.indexOf("msie") > -1;
            var isIE6 = _a.indexOf("msie 6.0") > -1;
            var isIE7 = _a.indexOf("msie 7.0") > -1;
            var isIE8 = _a.indexOf("msie 8.0") > -1;
            var isFirefox = _a.indexOf("firefox") > -1;
            var isChrome = _a.indexOf("chrome") > -1;
            var isOpera = _a.indexOf("opera") > -1;
            var isSafari = _a.indexOf("safari") > -1 && !isChrome;
            jQuery.MyBrowser = {
                isIE: isIE,
                isIE6: isIE6,
                isIE7: isIE7,
                isIE8: isIE8,
                isFirefox: isFirefox,
                isChrome: isChrome,
                isOpera: isOpera,
                isSafari:isSafari
            };
        })(jQuery)