判断浏览器类型

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