[erlang-questions] Erlang in the browser

Fredrik Svahn <>
Tue Jan 31 11:56:50 CET 2012

Hi Joe,

The Erlang list [1, 2, 3] is represented as js native objects {value:
1, next: {value: 2, next: {value: 3, next:nil}}}. The size of a string
represented as a list is 40 bytes per character in Chromium on my
x86_64 machine (I do not know if the size would be smaller on a 32 bit
machine). The corresponding number for beam is 16 bytes/char for
x86_64, I believe, so it is more wasteful as expected. I have
considered mapping it to js arrays but haven't done any measurements.
This is just a small script so I did not want to write my own GC, also
mapping to native objects is better if I later would like to make it
possible to compile performance critical beams to native javascript

The Erlang tuple {1,2,3} is represented as the js array [1, 2, 3].
Binaries are mapped to js strings, and atoms to numbers.

BR /Fredrik

On Tue, Jan 31, 2012 at 10:24 AM, Joe Armstrong <> wrote:
> Wow - ultra interesting.
> Just out of curiosity - how do you represent lists and tuples in JS?
> Are they represented
> as  native JS objects or as objects on the beam stack and heap? And if
> they are native JS objects what is the storage overhead of a
> list-cell?
> /Joe
> On Mon, Jan 30, 2012 at 10:14 PM, Fredrik Svahn <> wrote:
>> There is also http://svahne.github.com/browserl, a small script which
>> I wrote just for fun.
>> Short version: it is an Erlang emulator in javascript, which can load
>> and run an Erlang/OTP system from a tar file with ordinary beam files.
>> It can also load and execute individual beam files. It will run common
>> test and successfully complete some OTP test suites (the test suites
>> are not loaded in the example page, though). Files, binaries, ets and
>> floats are work in progress, at the moment they are only supported to
>> the extent needed to boot the system and run common test.
>> BR /Fredrik
>> On Tue, Nov 29, 2011 at 12:47 AM, Raoul Duke <> wrote:
>>> wow.
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