How can I detect which javascript engine (v8 or JSC) is used at runtime in Android?

Question

Newer versions of Android ( > 2.2) include the v8 javascript engine, while older versions only had JSC. However, according to http://blogs.nitobi.com/joe/2011/01/14/android-your-js-engine-is-not-always-v8/, which javascript engine is used at runtime seems to depend on an environment variable present at build-time (JS_ENGINE), as well as the hardware specs of the device:

# The default / alternative engine depends on the device class.
# On devices with a lot of memory (e.g. Passion/Sholes), the
# default is V8. On everything else, the only choice is JSC.

My question is this: is there any way that I can determine which javascript engine is in use from within a webpage, an embedded WebView, or an application?

If the answer is no, does anybody know which JS engine is used by the Android emulator?

---

The reason I'm asking this is because of this issue: http://code.google.com/p/android/issues/detail?id=12987

Basically, it may be that the javascript-to-java bridge in JSC is broken on Android 2.3.X, and this impacts the application I'm trying to write. I'm seeing a segfault from somewhere deep in the JNI on my emulator, but not on the handful of physical devices I've tested. I'm trying to determine if this is an emulator-only thing, a JSC-only thing, or something different altogether.

Answer 1

var s = '';
for (x in {
    3: 3,
    1: 1
  }) {
  s += x
}
if (s === '31') {
  alert('JSC');
} else {
  alert('V8');
}

By the way this will categorize Firefox as 'JSC' and newer IE versions will look like V8.

My blog post has more V8 sniffing tricks: http://erikcorry.blogspot.dk/2012/12/which-version-of-v8-do-i-have.html