这让我有了火狐的版本，

    let versionNumber = parseInt(window.navigator.userAgent.match(/Firefox\/([0- 
    9]+)\./)[1]);

我写这个是为了满足我的需要。

它可以获取信息，比如是否是移动设备或是否有视网膜显示器

试一试

var nav = {
        isMobile:function(){
            return (navigator.userAgent.match(/iPhone|iPad|iPod|Android|BlackBerry|Opera Mini|IEMobile/i) != null);
        },
        isDesktop:function(){
            return (navigator.userAgent.match(/iPhone|iPad|iPod|Android|BlackBerry|Opera Mini|IEMobile/i) == null);
        },
        isAndroid: function() {
            return navigator.userAgent.match(/Android/i);
        },
        isBlackBerry: function() {
            return navigator.userAgent.match(/BlackBerry/i);
        },
        isIOS: function() {
            return navigator.userAgent.match(/iPhone|iPad|iPod/i);
        },
        isOpera: function() {
            return navigator.userAgent.match(/Opera Mini/i);
        },
        isWindows: function() {
            return navigator.userAgent.match(/IEMobile/i);
        },
        isRetina:function(){
            return window.devicePixelRatio && window.devicePixelRatio > 1;
        },
        isIPad:function(){
            isIPad = (/ipad/gi).test(navigator.platform);
            return isIPad;
        },
        isLandscape:function(){
            if(window.innerHeight < window.innerWidth){
                return true;
            }
            return false;
        },
        getIOSVersion:function(){
            if(this.isIOS()){
                var OSVersion = navigator.appVersion.match(/OS (\d+_\d+)/i);
                OSVersion = OSVersion[1] ? +OSVersion[1].replace('_', '.') : 0;
                return OSVersion;
            }
            else
                return false;
        },
        isStandAlone:function(){
            if(_.is(navigator.standalone))
                return navigator.standalone;
            return false;
        },
        isChrome:function(){
            var isChrome = (/Chrome/gi).test(navigator.appVersion);
            var isSafari = (/Safari/gi).test(navigator.appVersion)
            return isChrome && isSafari;
        },
        isSafari:function(){
            var isSafari = (/Safari/gi).test(navigator.appVersion)
            var isChrome = (/Chrome/gi).test(navigator.appVersion)
            return !isChrome && isSafari;
        }
}

var ua = navigator.userAgent;

if (/Firefox\//.test(ua))
   var Firefox = /Firefox\/([0-9\.A-z]+)/.exec(ua)[1];

这是Fzs2和kennebec的更新，用于新边缘铬

function get_browser() { var ua=navigator.userAgent,tem,M=ua.match(/(opera|chrome|safari|firefox|msie|trident(?=\/))\/?\s*(\d+)/i) || []; if(/trident/i.test(M[1])){ tem=/\brv[ :]+(\d+)/g.exec(ua) || []; return {name:'IE',version:(tem[1]||'')}; } if(M[1]==='Chrome'){ tem=ua.match(/\bEdg\/(\d+)/) if(tem!=null) {return {name:'Edge(Chromium)', version:tem[1]};} tem=ua.match(/\bOPR\/(\d+)/) if(tem!=null) {return {name:'Opera', version:tem[1]};} } M=M[2]? [M[1], M[2]]: [navigator.appName, navigator.appVersion, '-?']; if((tem=ua.match(/version\/(\d+)/i))!=null) {M.splice(1,1,tem[1]);} return { name: M[0], version: M[1] }; } var browser=get_browser(); // browser.name = 'Edge(Chromium)' // browser.version = '86' console.log(browser);

使用这个:http://www.quirksmode.org/js/detect.html

alert(BrowserDetect.browser); // will say "Firefox"
alert(BrowserDetect.version); // will say "3" or "4"

这让我有了火狐的版本，

    let versionNumber = parseInt(window.navigator.userAgent.match(/Firefox\/([0- 
    9]+)\./)[1]);