A Javascript interpreter written in Javascript - no it's not a joke and with Zaphod to help you can run real web pages using it.

Mozilla Labs has been busy again. If you are looking for a Javascript engine to modify and extend then consider Narcissus. What is special about it is that it is written in standard Javascript - yes, Javascript in Javascript. This makes the engine very easy to modify and experiment with. The problem is how can you test your modifications?

This is where the new Zaphod comes in. If you install it then you can run scripts using Narcissus simply by marking the web page with a special tag “application/narcissus”. You can also run scripts through Narcissus by clicking the Mozilla button at the bottom right.

Notice that Narcissus doesn't replace the SpiderMonkey engine - in fact it's SpiderMonkey that runs the Narcissus code.

What would you use Narcissus/Zaphod for?

Apart from language experimentation it's is difficult to think of an immediate application. You could imagine the day when machines and implementations are so fast that you could run Narcissus as sort of virtual Javascript engine to iron out differences between browsers - but at the moment... 

In case you haven't noticed the names are apt - Narcissus because in Greek legend Narcissus fell in love with his own reflection - Javascript in Javascript - and Zaphod from Hitch Hiker's Guide had two heads.

If nothing else the idea of a Javascript interpreter written in Javascript should be something that keeps you awake at night.

To download Narcisus Download

Find out more about Zaphod

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