js判断游览器类型及版本号的代码_javascript技巧

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" };
}
}