ECMAScript support?!
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## ECMAScript support?!

Yes, there is some ECMAScript support in ELinks. There isn't anything we could call complete, but some bits could help with the most common ECMAScript usage cases - help you (and then us ;) get into your banking account, pass through those ignorant page redirects done by JavaScript code snippets and so.

ELinks does not have own ECMAScript parser and compiler; instead it reuses other people's work (this may eventually change, see the bottom of this file). First we aimed at the NJS engine, which is easy to install, small and compact; has nice naming scheme, horrible calling conventions and very lacking documentation; is not actively developed; and generally looks broken and extremely clumsy to work with. So we instead went the way of the SpiderMonkey (SM) engine (property of Mozilla), which is hard to install, bigger (mind you, it comes from Mozilla ;), has ugly naming scheme but nice calling conventions, acceptable documentation, is actively developed and ought to work.

### Ok, so how to get the ECMAScript support working?

Some systems come with either the SpiderMonkey installed or as an option. It would be good to test if you can take the easy path and let the system take care of installation through a package system. Below are listed instructions on what package you need to install on various systems (please help improve the list). If all goes well you can proceed to rebuilding ELinks.

On Debian testing (Etch) or unstable (SID), run the following:

    $ apt-get install libmozjs-dev

On Debian stable (Sarge), run the following:

    $ apt-get install libsmjs-dev

Installing the -dev package will automatically pull in the library package.

Once this is done, rebuild ELinks. The configure script should detect the SpiderMonkey library—check for this line in the features summary:

    ECMAScript (JavaScript) ......... SpiderMonkey document scripting

After following these instructions on a Debian system, you are done and should ignore the following directions.

The rest is only for non-Debian system.

Note that this procedure enables you to install SpiderMonkey, but in such a way that it might not work with anything else but ELinks. It is unlikely that anything else is ever going to use SpiderMonkey on your system, but if you want to take the safe way, get SM and follow the instructions in `src/README.html` instead. You will probably need to do some checkouting of bits of the Mozilla CVS tree and so, have fun.

To get SpiderMonkey source, go at ftp://ftp.mozilla.org/pub/mozilla.org/js/ and fetch the newest `js-` tarball there (`js-1.5-rc6a.tar.gz` at the time of writing this; you may try the RPMs, but we didn't test them).

    $ cd elinks
    $ wget ftp://ftp.mozilla.org/pub/mozilla.org/js/js-1.5-rc6a.tar.gz
    $ tar xvzf js-1.5-rc6a.tar.gz

Next, you need to patch it so that you will have any chance to install it as you fetched it. Grab it in ELinks at `contrib/js-1.5-rc6a+elinks.patch` (if you have a different version, still try to go ahead, you might have some success), then go to the SpiderMonkey directory (called js) and apply it as

    $ cd js
    $ patch -p1 <../contrib/js-1.5-rc6a+elinks.patch
    $ cd src

Now, edit config.mk and adjust the `$PREFIX` variable - you probably won't like the default value - ELinks will find it there, but your dynamic linker likely won't.

E.g., for /usr/local installation:

    $ sed 's#^PREFIX = /opt/spidermonkey#PREFIX = /usr/local#' < config.mk > config.mk.t
    $ mv -f config.mk.t config.mk

Now you can finally go for it:

    $ make -f Makefile.ref
    $ make -f Makefile.ref export

Now install it:

    $ su -c 'make -f Makefile.ref install && (ldconfig -v | grep libjs)'

Check for:

    libjs.so -> libjs.so

If you don't get such result, check that the library's installation path (e.g. /usr/local/lib) is present in /etc/ld.so.conf (man 8 ldconfig).

If all went well, you can proceed to rebuild ELinks now. If something broke, see you on #elinks @ FreeNode or in the mailing list. You may add your options to `./configure` as usual; SpiderMonkey should be autodetected.

    $ cd ../..
    $ ./configure

Check for the following line in the features summary:

    ECMAScript (JavaScript) ......... SpiderMonkey document scripting

Then run:

    $ make
    $ su -c 'make install'

Enjoy.

### The ECMAScript support is buggy! Shall I blame Mozilla people?

Likely not. The ECMAScript engine provides only the language compiler and some basic built-in objects, and it's more than likely that the problem is on our side in the implementation of some of the HTML/DOM objects (perhaps we just haven't bothered to implement it at all yet). So better tell us first, and if we think it's not our fault we will tell you to go complain to Mozilla (better yet if it does not work in the Mozilla browsers neither ;-).

### Now, I would still like NJS or a new JS engine from scratch…

...and you don't fear some coding? That's fine then! ELinks is in no way tied to SpiderMonkey, in fact the ECMAScript support was carefully implemented so that there are no SpiderMonkey references outside of `src/ecmascript/spidermonkey.*`. If you want to implement an alternative ECMAScript backend, go ahead - you will just need to write an autoconf detection for it and tie it to `src/ecmascript/ecmascript.c`, which should be easy. We await your patches eagerly.

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