JS 客户端检测
2024-09-04 10:16:47
能力检测
能力检测的目标不是识别特定的浏览器，而是识别浏览器的能力。
能力检测需要注意两点：
- 先检测达成目的的最常用的特性。因为先检测最常用的特性可以保证代码最优化，因为在多数情况下都可以避免测试多个条件
- 必须测试实际要用到的特性。
举例来说，检测某个属性是否存在并不能确定对象是否支持排序。看了下面的代码，得到的结论就是尽量使用typeof进行能力检测
function isSortable(object) {
return !!object.sort;//这样做是不取的 这不是能力检测 只检测是否存在相应的方法
}
//如果用上面的方法 那下面的demo不是...
var result = isSortable({ sort: true });
//这样更好，因为实际检测了sort是否为函数
function isSortable(object) {
return typeof object.sort == 'function';
}
下面的这个方法是相应来说检测能力比较保险的方式
/*
*@desc:在浏览器环境下测试任何对象的某个特性是否存在
*/
function isHostMethod(object,property) {
var t = typeof object[property];
return t == 'function' || (!!(t == 'object' && object[property])) || t == 'unknown';
}
下面的这个demo是检测浏览器是否支持Netscape 风格的插件和是否具有DOM1 级规定的能力
//need to wait until onload so body is available
window.onload = function(){ function getWindowWidth(){
if (window.innerWidth){
return window.innerWidth;
} else if (document.documentElement.clientWidth){
return document.documentElement.clientWidth;
} else if (document.body.clientWidth){
return document.body.clientWidth;
}
} //determine if the browser has Netscape-style plugins
var hasNSPlugins = !!(navigator.plugins && navigator.plugins.length); //determine if the browser has basic DOM Level 1 capabilities
var hasDOM1 = !!(document.getElementById && document.createElement &&
document.getElementsByTagName); alert("Window width: " + getWindowWidth());
alert("Supports Netscape plugins? " + hasNSPlugins);
alert("Supports Core DOM 1? " + hasDOM1);
}
怪癖检测
IE8及更早版本的怪癖：如果某个实例属性与[Enumerable]标识为false的某个原型属性同名，那个该实例属性将不会出现在for-in循环中
var hasDontEnumQuirk = function(){
var o = { toString : function(){} };
for (var prop in o){
if (prop == "toString"){
return false;
}
}
return true;
}();
alert(hasDontEnumQuirk);
Safari3怪癖：会枚举被隐藏的属性
var hasEnumShadowsQuirk = function(){
var o = { toString : function(){} };
var count = 0;
for (var prop in o){
if (prop == "toString"){
count++;
}
}
return (count > 1);
}();
alert(hasEnumShadowsQuirk);
用户代码检测
用到的client.js文件如下：
var client = function(){
//rendering engines
var engine = {
ie: 0,
gecko: 0,
webkit: 0,
khtml: 0,
opera: 0,
//complete version
ver: null
};
//browsers
var browser = {
//browsers
ie: 0,
firefox: 0,
safari: 0,
konq: 0,
opera: 0,
chrome: 0,
//specific version
ver: null
};
//platform/device/OS
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 (window.opera){
engine.ver = browser.ver = window.opera.version();
engine.opera = browser.opera = parseFloat(engine.ver);
} else if (/AppleWebKit\/(\S+)/.test(ua)){
engine.ver = RegExp["$1"];
engine.webkit = parseFloat(engine.ver);
//figure out if it's Chrome or Safari
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
};
}();
浏览器检测的demo HTML页面的js代码如下：
<!DOCTYPE html>
<html>
<head>
<title>User-agent Detection Example</title>
<script type="text/javascript" src="client.js"></script>
</head>
<body>
<h2>Rendering Engines</h2>
<ul>
<li>client.engine.ie =
<script>document.write(client.engine.ie);</script></li>
<li>client.engine.webkit =
<script>document.write(client.engine.webkit);</script></li>
<li>client.engine.gecko =
<script>document.write(client.engine.gecko);</script></li>
<li>client.engine.khtml =
<script>document.write(client.engine.khtml);</script></li>
<li>client.engine.opera =
<script>document.write(client.engine.opera);</script></li>
<li>client.engine.ver =
<script>document.write(client.engine.ver);</script></li> </ul>
<h2>Browsers</h2>
<ul>
<li>client.browser.ie =
<script>document.write(client.browser.ie);</script></li>
<li>client.browser.safari =
<script>document.write(client.browser.safari);</script></li>
<li>client.browser.firefox =
<script>document.write(client.browser.firefox);</script></li>
<li>client.browser.konq =
<script>document.write(client.browser.konq);</script></li>
<li>client.browser.opera =
<script>document.write(client.browser.opera);</script></li>
<li>client.browser.chrome =
<script>document.write(client.browser.chrome);</script></li>
<li>client.browser.ver =
<script>document.write(client.browser.ver);</script></li>
</ul> <h2>System</h2>
<ul>
<li>client.system.win =
<script>document.write(client.system.win);</script></li>
<li>client.system.mac =
<script>document.write(client.system.mac);</script></li>
<li>client.system.x11 =
<script>document.write(client.system.x11);</script></li>
<li>client.system.iphone =
<script>document.write(client.system.iphone);</script></li>
<li>client.system.ipod =
<script>document.write(client.system.ipod);</script></li>
<li>client.system.ipad =
<script>document.write(client.system.ipad);</script></li>
<li>client.system.ios =
<script>document.write(client.system.ios);</script></li>
<li>client.system.android =
<script>document.write(client.system.android);</script></li>
<li>client.system.nokiaN =
<script>document.write(client.system.nokiaN);</script></li>
<li>client.system.winMobile =
<script>document.write(client.system.winMobile);</script></li>
<li>client.system.wii =
<script>document.write(client.system.wii);</script></li>
<li>client.system.ps =
<script>document.write(client.system.ps);</script></li>
</ul>
<center> </center>
</body>
</html>
总结一下：
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