Pick up the Android version in the browser by Javascript

I'm building a web app and wanting to disable transitions effects on Android devices under version 3.0.

Is there anyway to pick up the Android version number by Javascript in the browser? If so how?

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

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

You can look at the user agent string - window.navigator.userAgent described here: https://developer.mozilla.org/en/DOM/window.navigator.userAgent

If what you're really trying to detect is whether you have a version of the browser that supports a particular feature, then it's nearly always better to use feature detection instead of browser version detection. modernizr is a huge base of code for feature detection that you can either use as is or borrow one particular piece from or just learn how the general technique works.

When I Google, I see user agent strings like this for Android:

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

A regex of /Android\s+([\d\.]+)/ on window.navigator.userAgent will pick up the Android version number.

Motorola's player user agents can have the following:

Linux;Android ; Release/4.1.2

So, I've had to start using the the following regex:

[a|A]ndroid[^\d]*([\d[_|.]]+\d)

This code checks the full version of Android from the useragent.

var test = LowerThanAndroidVersion('4.4');
if (test) {
    alert('lower than android 4.4')
} else if (test == undefined) {
    alert('no android')
} else {
    alert('android 4.4 or higher');
}    

function LowerThanAndroidVersion(testversion) {
    //var useragent = 'Mozilla/5.0 (Linux; U; Android 4.3.1; en-gb; GT-I9300 Build/IMM76D) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30';
    var useragent = navigator.userAgent;
    var androidpoint = useragent.indexOf('Android');
    if (androidpoint >= 0) {
        var rest = useragent.substring(androidpoint + 8, useragent.length);
        var version = rest.substring(0, rest.indexOf(';'));
        return (version < testversion) ? true : false;
    }
}

I made this function and worked very well in Android 2.6.3, 4.2.2., 6.0.1 in different browsers and devices. I think that can be an alternative.

function check_android_version()
{
    var ua = navigator.userAgent; 
    ua = ua.toLowerCase();

    var and_pos = ua.search("android");
    if(and_pos == -1)
	    return 0; //not android
	
    var pv_pos = ua.indexOf(";", and_pos);
    var versao = ua.slice(and_pos+8, pv_pos);

    return versao;
}

This is quite simple, first, search for the word "android". If not found, returns 0 (is not an Android user agent). Then search for the first ';' after the "android" position that marks the end of the version. Once these positions are gotten, the 'slice' insulates the version numbers (that '+8' removes the word "android" of the final result) an then returns.

If someone find any flaw, would be nice to share.

It's better to check first if device is android or not as Windows mobile can have Android in its user agent.

Example: Mozilla/5.0 (Windows Phone 10.0; Android 4.2.1; ; ) AppleWebKit/ (KHTML, like Gecko) Chrome/ Mobile Safari/ Edge/.

Here is way to check it https://stackoverflow.com/questions/21741841/detecting-ios-android-operating-system

1- Windows phone introduced a fake "android" user agent, so this deal with it
2- As @andy pointed out, there are some models with this format: Android/#.##
3- You can use the flag /i for case-insensitive
4- This code gives you back NaN when its not android and the version as a float when it is.
5- If you find more fake android phones you only need to add the string like this: (?:windows phone|fake phone|android...........

alert( parseFloat(navigator.userAgent.match(/.*?(?:windows phone|android\D+([0-9\.]*))|()/i)[1]) );