Pick up the Android version in the browser by Javascript

function getAndroidVersion(ua) {
    ua = (ua || navigator.userAgent).toLowerCase(); 
    var match = ua.match(/android\s([0-9\.]*)/i);
    return match ? match[1] : undefined;
};

getAndroidVersion(); //"4.2.1"
parseInt(getAndroidVersion(), 10); //4
parseFloat(getAndroidVersion()); //4.2