JS自动识别浏览器

可以识别浏览器类型及版本号，

var userAgent = navigator.userAgent, 
    rMsie = /(msie\s|trident.*rv:)([\w.]+)/,        //IE
    rFirefox = /(firefox)\/([\w.]+)/,           //Firefox
    rOpera = /(opera).+version\/([\w.]+)/,      //Opera
    rChrome = /(chrome)\/([\w.]+)/,             //Chrome
    rMicromessenger = /(micromessenger)\/([\w.]+)/,     //微信
    rSafari = /version\/([\w.]+).*(safari)/;
    var browser;
    var version;
    function uaMatch(ua) {    
        var match = rMsie.exec(ua);
        if (match != null) {
            return { browser : "IE", version : match[2] || "0" };
        } 
        var match = rFirefox.exec(ua);
        if (match != null) {
            return { browser : match[1] || "", version : match[2] || "0" };
        } 
        var match = rOpera.exec(ua);
        if (match != null) {
            return { browser : match[1] || "", version : match[2] || "0" };
        }
        var match = rChrome.exec(ua);
        if (match != null) {
            return { browser : match[1] || "", version : match[2] || "0" };
        }
        var match = rMicromessenger.exec(ua);
        if (match != null) {
            return { browser : match[1] || "", version : match[2] || "0" };
        }
        var match = rSafari.exec(ua);
        if (match != null) {
            return { browser : match[2] || "", version : match[1] || "0" };
        }
        if (match != null) {
            return { browser : "", version : "0" };
        }
    } 
    var browserMatch = uaMatch(userAgent.toLowerCase());
        if (browserMatch.browser) 
    {
        browser = browserMatch.browser;
        version = browserMatch.version;
        }
    alert(browser+version);