navigator.userAgent 判断当前浏览器所处的环境

场景1：判断页面是在手机端还是PC端打开

window.location.href=/Android|webOS|iPhone|iPod|BlackBerry/i.test(navigator.userAgent)?"http://localhost:8888/mobile_web":"http://localhost:8888/PC";

场景2：判断页面是在手机端，平板端还是PC端打开

var os = function (){
    var ua = navigator.userAgent,
    isWindowsPhone = /(?:Windows Phone)/.test(ua),
    isSymbian = /(?:SymbianOS)/.test(ua) || isWindowsPhone,
    isAndroid = /(?:Android)/.test(ua),
    isFireFox = /(?:Firefox)/.test(ua),
    isChrome = /(?:Chrome|CriOS)/.test(ua),
    isTablet = /(?:iPad|PlayBook)/.test(ua) || (isAndroid && !/(?:Mobile)/.test(ua)) || (isFireFox && /(?:Tablet)/.test(ua)),
    isPhone = /(?:iPhone)/.test(ua) && !isTablet,
    isPc = !isPhone && !isAndroid && !isSymbian;
    return {
        isTablet: isTablet,
        isPhone: isPhone,
        isAndroid: isAndroid,
        isPc: isPc
    };    
}();
 
if (os.isAndroid || os.isPhone) {   
   alert("手机" );
} else if (os.isTablet) {
    alert("平板" );
} else if (os.isPc) {
    alert("电脑" );
}

场景3：获取操作系统类型，判断是Android或者IOS

/**
     * 获取操作系统类型，
     * 0 Android
     * 1 iOS
     */
    function getOSType() {
        if (/(Android)/i.test(navigator.userAgent)) {
            return 0;
        } else if (/(iPhone|iPad|iPod|iOS)/i.test(navigator.userAgent)) {
            return 1;
        } else {
            return 2;
        }
    }

场景4：判断当前环境是否是微信环境

function is_weixin(){
      var ua = navigator.userAgent.toLowerCase();
      if(ua.match(/MicroMessenger/i)=="micromessenger") {
           return true;
     } else {
            return false;
      }
}