[js]判断浏览器

sys_userAgent.js

function sys_userAgent(){ 
    var userAgent = navigator.userAgent,     
    rMsie = /(msie\s|trident.*rv:)([\w.]+)/,     
    rFirefox = /(firefox)\/([\w.]+)/,     
    rOpera = /(opera).+version\/([\w.]+)/,     
    rChrome = /(chrome)\/([\w.]+)/,     
    rSafari = /version\/([\w.]+).*(safari)/;    
    var browser,version,ua;    
    ua = userAgent.toLowerCase();    

    var match = rMsie.exec(ua);    
    if (match != null) {    
        return { browser : "ie", version : match[2] || "0" };    
    } 
     
    if (!!window.ActiveXObject || "ActiveXObject" in window){ 
        return { browser : "ie", version : "0"};     
    } 
     
    var match = rFirefox.exec(ua);    
    if (match != null) {    
        return { browser : "firefox", version : match[2] || "0" };    
    }    

    var match = rOpera.exec(ua);    
    if (match != null) {    
        return { browser : "opera", version : match[2] || "0" };    
    }    

    var match = rChrome.exec(ua);    
    if (match != null) {    
        return { browser : "chrome", version : match[2] || "0" };    
    }    

    var match = rSafari.exec(ua);    
    if (match != null) {    
        return { browser : "safari", version : match[1] || "0" };    
    }    

    if (match != null) {    
        return { browser : "", version : "0" };    
    } 
}