使用navigator.userAgent来判断浏览器的类型

正则表达式匹配
function userBrowser(){
    var browserName=navigator.userAgent.toLowerCase();
    if(/msie/i.test(browserName) && !/opera/.test(browserName)){
        alert("IE");
        return ;
    }else if(/firefox/i.test(browserName)){
        alert("Firefox");
        return ;
    }else if(/chrome/i.test(browserName) && /webkit/i.test(browserName) && /mozilla/i.test(browserName)){
        alert("Chrome");
        return ;
    }else if(/opera/i.test(browserName)){
        alert("Opera");
        return ;
    }else if(/webkit/i.test(browserName) &&!(/chrome/i.test(browserName) && /webkit/i.test(browserName) && /mozilla/i.test(browserName))){
        alert("Safari");
        return ;
    }else{
        alert("unKnow");
    }
}

var sUserAgent = navigator.userAgent;

//检测是否Opera浏览器
var isOpera = sUserAgent.indexOf("Opera")>-1

//检测是否Safari
var isKHTML = sUserAgent.indexOf("KHTML")>-1
                || sUserAgent.indexOf("Konqueror")>-1
                || sUserAgent.indexOf("AppleWebKit")>-1;

//检测IE
var isIE = sUserAgent.indexOf("compatible") > -1
            &&sUserAgent.indexOf("MSIE") > -1
            &&!isOpera;

//检测Firfox
var isFF = sUserAgent.indexOf("Firefox")>-1&&!isKHTML;

//检测Chrome浏览器
var isChrome = sUserAgent.indexOf("AppleWebKit")>-1;