Pick up the Android version in the browser by Javascript

I can't comment because I don't have enough rep... Just wanted to add that I had to change neiker's code to

var match = ua.match(/Android\s([0-9\.]*)/i);

to make it case insensitive because the Galaxy S3 was returning "android" instead of Android in its user agent

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

Use below code to get 2 digit version of Android

var ua = navigator.userAgent;
if( ua.indexOf("Android") >= 0 )
{
  var androidversion = parseFloat(ua.slice(ua.indexOf("Android")+8)); 
  if (androidversion < 2.3)
  {
      // do whatever
  }
}

For example

Mozilla/5.0 (Linux; U; Android 2.2.1; fr-ch; A43 Build/FROYO) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1

will return Android Version = 2.2