js获取客户端浏览器信息及版本

<script type="text/javascript">
    var agent = navigator.userAgent.toLowerCase();
    function getBrowserInfo() {
        alert(agent);
        var regStr_ie = /msie [\d.]+;/gi;
        var regStr_ff = /firefox\/[\d.]+/gi
        var regStr_chrome = /chrome\/[\d.]+/gi;
        var regStr_saf = /safari\/[\d.]+/gi;
        //IE
        //Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
        if (agent.indexOf("msie") > 0) {
            return agent.match(regStr_ie);
        }

        //firefox
        //Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0
        if (agent.indexOf("firefox") > 0) {
            return agent.match(regStr_ff);
        }
        //Safari
        if (agent.indexOf("safari") > 0 && agent.indexOf("chrome") < 0) {
            return agent.match(regStr_saf);
        }
        //Chrome
        //Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.108 Safari/537.36
        if (agent.indexOf("chrome") > 0) {
            return agent.match(regStr_chrome);
        }
    }

    //（2）然后获取版本号

    var browser = getBrowserInfo();
    var ie;
    if (browser == null || browser == "" || browser.length == 0) {
        //获取rv的值
        //alert(agent);
        var regStr = /rv\:[\d.]+/gi;
        var rv = agent.match(regStr);
        //alert(rv);

        var ie = (rv + "").split(':')[1];
        //alert(ie);
    }
    else {
        var verinfo = (browser + "").replace(/[^0-9.]/ig, "");
        ie = verinfo;
    }
    //ie版本小于9的浏览器,现在不管其他浏览器，只管ie
    if (ie<9) {
        alert("测试成功");
    }
    
    //alert(ie);
</script>