Jem.js

Just Erlang Maps for Javascript

Why Jem.js?

Using JSON to communicate with an erlang server requires using resources to parse it and takes up more bandwidth than needed. Instead of sending plaintext JSON, you can use Jem.js to encode your JavaScript objects in the native Erlang binary format, so that, from the server, all that's needed is calling erlang:binary_to_term(Binary) to obtain the same representation of a JSON you would usually get from jiffy.

So why would you use this? You can save money on the hosting.

How to use it?

The 2 functions Jem.js exposes are pretty straight forward and you can find usage examples in the examples directory (or even better, just try using this Fiddle).

From the erlang side it's just as simple, all you need to do is replace jiffy:decode/1 and jiffy:encode/1 with binary_to_term/1 and term_to_binary/1.

For example, lets say we have this pretty straight forward Cowboy endpoint:

handle_post(Req, State) ->
  {ok, Body, Req1} = cowboy_req:body(Req),
  Decoded = jiffy:decode(Body, [return_maps]),
  Reply = do_whatever(Decoded),
  {jiffy:encode(Reply), Req1, State}.

With jem.js on the client, we could instead do this:

handle_post(Req, State) ->
  {ok, Body, Req1} = cowboy_req:body(Req),
  Decoded = erlang:binary_to_term(Body),
  Reply = do_whatever(Decoded),
  {erlang:term_to_binary(Reply), Req1, State}.

(just remember you are not accepting application/json but application/erlang on the content types)

Contact Us

For questions or general comments regarding the use of this library, please use our public hipchat room.

If you find any bugs or have a problem while using this library, please open an issue in this repo (or a pull request :)).

And you can check all of our open-source projects at inaka.github.io.