判断是否为ie浏览器

function isIE(){
    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; 
    var version; 
    var ua = userAgent.toLowerCase(); 

    var match = rMsie.exec(ua);    
    if (match != null) {  
        ieVersion = { browser : "IE", version : match[2] || "0" };
        return true; 
    }  
    var match = rFirefox.exec(ua);  
    if (match != null) {  
        var ffVersion = { browser : match[1] || "", version : match[2] || "0" };
        return false; 
    }  
    var match = rOpera.exec(ua);  
    if (match != null) { 
       var opVersion =  { browser : match[1] || "", version : match[2] || "0" };
       return false;
    }  
    var match = rChrome.exec(ua);  
    if (match != null) {  

        var chVersion = { browser : match[1] || "", version : match[2] || "0" };
        return false;
    }  
    var match = rSafari.exec(ua);  
    if (match != null) {  

       var sfVersion = { browser : match[2] || "", version : match[1] || "0" }; 
       return false;
    }  
    if (match != null) {  
        var ohterVersion = { browser : "", version : "0" }; 
        return false;
    }
}