浏览器探针--JavaScript

在开发中，我们经常会遇到需要判断操作平台和浏览器类型的问题。

HTTP规范（包括1.0和1.1版）明确规定，浏览器应该发送简短的用户代理字符串，指明浏览器的名称和版本号。

RFC 2616 (即HTTP1.1协议规范）是这样描述用户代理字符串的：

“产品标识符常用于通信应用程序标识自身，由软件名和版本组成。使用产品标识符的大多数领域也允许列出作为应用程序主要部分的子产品，由空格分隔。按照惯例，产品要按照相应的重要程度依次列出，以便标识应用程序。”

上述规范进一步规定，用户代理字符串应该以一组产品的形式给出，字符串格式为：标识符/产品 版本号。

常用浏览器的UA信息

浏览器	UA信息
IE	“Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; rv:11.0) like Gecko”
Firefox	“Mozilla/5.0 (Windows NT 6.1; WOW64; rv:46.0) Gecko/20100101 Firefox/46.0”
Chrome	“Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36”
Safari	“Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/601.5.17 (KHTML, like Gecko) Version/9.1 Safari/601.5.17”
Opera	“Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.84 Safari/537.36 OPR/38.0.2220.31”
Edge	“Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2486.0 Safari/537.36 Edge/13.10586”

一、传统示例

网上随便一搜，会出现很多解决方案。但是往往都不健全，比如：

function myBrowser(){
var userAgent = navigator.userAgent; //取得浏览器的userAgent字符串
if (userAgent.indexOf("Opera") > -1) {
//判断是否Opera浏览器
return "Opera"
}
if (userAgent.indexOf("Firefox") > -1) {
//判断是否Firefox浏览器
return "FF";
}
if (userAgent.indexOf("Chrome") > -1){
//判断是否Chrome浏览器
return "Chrome";
}
if (userAgent.indexOf("Safari") > -1) {
//判断是否Safari浏览器
return "Safari";
}
if (userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1){
//判断是否IE浏览器
return "IE";
}
}

通过对比上述UA，可得知，其上述示例写的并不好，由于“Chrome浏览器UA”和“Safari浏览器UA”中都包含“Safari”字样，且“Chrome浏览器UA”和“Edge浏览器UA”中都包含“Chrome”字样，上述之所以可以正确判断Safari，完全是因为把“Safari”的判断写到了“Chrome”后面，且使用if…if判断，而非if…else if判断。这样的写法很危险，所以个人认为其不够健全、不够优雅。

二、更加优雅的示例

var client = function(){
//渲染引擎
var engine = {
ie: 0,
gecko: 0,
webkit: 0,
khtml: 0,

//complete version
ver: null
};

//浏览器
var browser = {
//browsers
ie: 0,
firefox: 0,
safari: 0,
konq: 0,
opera: 0,
chrome: 0,
edge: 0,

//specific version
ver: null
};

//系统
var system = {
win: false,
mac: false,
x11: false,

//mobile devices
iphone: false,
ipod: false,
ipad: false,
ios: false,
android: false,
nokiaN: false,
winMobile: false,

//game systems
wii: false,
ps: false
};

//detect rendering engines/browsers
var ua = navigator.userAgent;
if (/AppleWebKit\/(\S+)/.test(ua)){
engine.ver = RegExp["$1"];
engine.webkit = parseFloat(engine.ver);

//figure out if it's Chrome or Safari or opera or edge
if(/OPR\/(\S+)/.test(ua)){
browser.ver = RegExp["$1"];
browser.opera = parseFloat(browser.ver);
}else if(/Edge\/(\S+)/.test(ua)){
browser.ver = RegExp["$1"];
browser.edge = parseFloat(browser.ver);
} else if (/Chrome\/(\S+)/.test(ua)){
browser.ver = RegExp["$1"];
browser.chrome = parseFloat(browser.ver);
} else if (/Version\/(\S+)/.test(ua)){
browser.ver = RegExp["$1"];
browser.safari = parseFloat(browser.ver);
} else {
//approximate version
var safariVersion = 1;
if (engine.webkit < 100){
safariVersion = 1;
} else if (engine.webkit < 312){
safariVersion = 1.2;
} else if (engine.webkit < 412){
safariVersion = 1.3;
} else {
safariVersion = 2;
}
browser.safari = browser.ver = safariVersion;
}
} else if (/KHTML\/(\S+)/.test(ua) || /Konqueror\/([^;]+)/.test(ua)){
engine.ver = browser.ver = RegExp["$1"];
engine.khtml = browser.konq = parseFloat(engine.ver);
} else if (/rv:([^\)]+)\) Gecko\/\d{8}/.test(ua)){
engine.ver = RegExp["$1"];
engine.gecko = parseFloat(engine.ver);

//determine if it's Firefox
if (/Firefox\/(\S+)/.test(ua)){
browser.ver = RegExp["$1"];
browser.firefox = parseFloat(browser.ver);
}
} else if (/MSIE ([^;]+)/.test(ua)){
engine.ver = browser.ver = RegExp["$1"];
engine.ie = browser.ie = parseFloat(engine.ver);
}

//detect browsers
browser.ie = engine.ie;
browser.opera = engine.opera;

//detect platform
var p = navigator.platform;
system.win = p.indexOf("Win") == 0;
system.mac = p.indexOf("Mac") == 0;
system.x11 = (p == "X11") || (p.indexOf("Linux") == 0);

//detect windows operating systems
if (system.win){
if (/Win(?:dows )?([^do]{2})\s?(\d+\.\d+)?/.test(ua)){
if (RegExp["$1"] == "NT"){
switch(RegExp["$2"]){
case "5.0":
system.win = "2000";
break;
case "5.1":
system.win = "XP";
break;
case "6.0":
system.win = "Vista";
break;
case "6.1":
system.win = "7";
break;
default:
system.win = "NT";
break;
}
} else if (RegExp["$1"] == "9x"){
system.win = "ME";
} else {
system.win = RegExp["$1"];
}
}
}

//mobile devices
system.iphone = ua.indexOf("iPhone") > -1;
system.ipod = ua.indexOf("iPod") > -1;
system.ipad = ua.indexOf("iPad") > -1;
system.nokiaN = ua.indexOf("NokiaN") > -1;

//windows mobile
if (system.win == "CE"){
system.winMobile = system.win;
} else if (system.win == "Ph"){
if(/Windows Phone OS (\d+.\d+)/.test(ua)){;
system.win = "Phone";
system.winMobile = parseFloat(RegExp["$1"]);
}
}

//determine iOS version
if (system.mac && ua.indexOf("Mobile") > -1){
if (/CPU (?:iPhone )?OS (\d+_\d+)/.test(ua)){
system.ios = parseFloat(RegExp.$1.replace("_", "."));
} else {
system.ios = 2;  //can't really detect - so guess
}
}

//determine Android version
if (/Android (\d+\.\d+)/.test(ua)){
system.android = parseFloat(RegExp.$1);
}

//gaming systems
system.wii = ua.indexOf("Wii") > -1;
system.ps = /playstation/i.test(ua);

//return it
return {
engine:     engine,
browser:    browser,
system:     system
};
}();