JS判断浏览器类型

 var userAgent = navigator.userAgent;

var isSafari = /Safari/.test(userAgent) && !/Chrome/.test(userAgent);
if (isSafari) {
    document.write("<p style='color:red'>Your browser does not support the video tag, please use one of Firefox / Chrome / IE 9 or above</p><br>");
}

var isIE = userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1; 
if (isIE && !isSafari) {
    var reIE = new RegExp("MSIE (\\d+\\.\\d+);");
    reIE.test(userAgent);
    var fIEVersion = parseFloat(RegExp["$1"]);
    if (fIEVersion <= 8) {
        document.write("<p style='color:red'>Your browser does not support the video tag, please use one of Firefox / Chrome / IE 9 or above.</p><br>");
    } 
}