js客户端检测

客户端检测方式

• 能力检测
• 怪癖检测
• 用户代理检测

能力检测

1.  if(object.propertyInQuestion){
        // 使用object.propertyInQuestion
    }

   • 先检测达成目的的最常用的特性
   • 必须测试实际要用到的特性，一个特性存在，不一定意味着另一个特性也存在

2.  // 检查sort是不是函数
    function isSortable(object){
        return typeof object.sort == "function";
    }

3. // 确定浏览器是否支持Netspace风格的插件
   var hasNSPlugins = !!(navigator.plugins && navigator.pligins.length);
   // 确定浏览器是否具有DOM1级别规定的能力
   var hasDOM1 = !!(document.getElementById && document.createElement && document.getElementByTagName);

怪癖检测

  var hasDontEnumQuik = function(){
      var o = {toString : function(){}};
      for(var props in o){
          if (props == "toString"){ 
              return false ;  
          }
      }
      return true;
  }();

用户代理检测

    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        
        };