如果Java applet无法运行，则执行JavaScript

Question

I have a web page with an embedded Java applet that connects to a server on my LAN for the purpose of measuring LAN Speed. The reason I am using a Java applet is because as far as I am aware, Javascript is too inaccurate to use for measuring LAN Speed.

However, I do have an (inaccurate) javascript version that can do a really rough LAN Speed measurement.

How can I tell if the applet successfully ran, and if not, to execute the javascript fallback speed test? I'm using Java 8 and Google Chrome 36.

Here's what I've tried:

<applet id="SpeedTester" code="SpeedTester.class" archive="SpeedTester.jar"> 
    <param...>
    <param...>
    <param...>
    <script>alert("Applet Failed to Execute!"); runJSSpeedTest();</script>
</applet>

However, it seems as though the code in <script> always runs regardless of if Java is installed, disabled, or enabled.

Answer 1

The applet should provide a method to confirm it loaded OK. A JS should poll the applet for a time, trying each time to access that method with an 'OK' result. It the JS has not received an 'OK' after a certain time limit, use the JS speed test.