JS 按 UA 识别浏览器

// http://www.cnblogs.com/vajoy/p/3736576.html
var userAgent = navigator.userAgent, 
                rMsie = /(msie\s|trident\/7)([\w.]+)/, 
                rTrident = /(trident)\/([\w.]+)/, 
                rFirefox = /(firefox)\/([\w.]+)/, 
                rOpera = /(opera).+version\/([\w.]+)/, 
                rNewOpera = /(opr)\/(.+)/, 
                rChrome = /(chrome)\/([\w.]+)/, 
                rSafari = /version\/([\w.]+).*(safari)/;
var matchBS,matchBS2;
var browser;
var version;
var ua = userAgent.toLowerCase();
var uaMatch = function(ua) {
    matchBS = rMsie.exec(ua);
    if (matchBS != null) {
        matchBS2 = rTrident.exec(ua);
        if (matchBS2 != null){
            switch (matchBS2[2]){
                case "4.0": return { browser : "IE", version : "8" };break;
                case "5.0": return { browser : "IE", version : "9" };break;
                case "6.0": return { browser : "IE", version : "10" };break;
                case "7.0": return { browser : "IE", version : "11" };break;
                default:return { browser : "IE", version : "undefined" };
            }
        }
        else
        return { browser : "IE", version : matchBS[2] || "0" };
    }
    matchBS = rFirefox.exec(ua);
    if ((matchBS != null)&&(!(window.attachEvent))&&(!(window.chrome))&&(!(window.opera))) {
        return { browser : matchBS[1] || "", version : matchBS[2] || "0" };
    }
    matchBS = rOpera.exec(ua);
    if ((matchBS != null)&&(!(window.attachEvent))) {
        return { browser : matchBS[1] || "", version : matchBS[2] || "0" };
    }
    matchBS = rChrome.exec(ua);
    if ((matchBS != null)&&(!!(window.chrome))&&(!(window.attachEvent))) {
        matchBS2 = rNewOpera.exec(ua);
        if(matchBS2 == null)
        return { browser : matchBS[1] || "", version : matchBS[2] || "0" };
        else
        return { browser : "Opera", version : matchBS2[2] || "0" };
    }
    matchBS = rSafari.exec(ua);
    if ((matchBS != null)&&(!(window.attachEvent))&&(!(window.chrome))&&(!(window.opera))) {
        return { browser : matchBS[2] || "", version : matchBS[1] || "0" };
    }
    if (matchBS != null) {
        return { browser : "undefined", version : " browser" };
    }
}
var browserMatch = uaMatch(userAgent.toLowerCase());
if (browserMatch.browser) {
    browser = browserMatch.browser;
    version = browserMatch.version;
}
console.log(browser+version);