erlang_v8_lib

An opinionated JavaScript framework built on top of erlang_v8. erlang_v8_lib is an Erlang application that includes a small framework to simplify the task of adding functionality to the scripting environment.

The app adds three major components to accomplish this:

• A v8 worker pool
• A simple module system that makes it easy to connect JavaScript and Erlang.
• A few batteries included modules

Getting started

Compile and start a shell:

$ make
$ make shell

Ensure that all required applications have been started, start the lib supervisor (note that this is a separate and mandatory step. the reasoning will be outlined below) and run some code:

1>  application:ensure_all_started(erlang_v8_lib).
{ok, [...]}
2> erlang_v8_lib_sup:start_link().
{ok,<0.69.0>}
3> erlang_v8_lib:run(<<"process.return(1 + 1)">>).
{ok,2}

Registering handlers

A handler is an erlang module that exposes a run/2 function that is registered with an identifier:

-module(my_handler).

-export([run/2]).

run(_Args, _HandlerContext) ->
    {ok, <<"hello">>}.

Registering the module as {<<"myhandler">>, my_handler} (more docs inc) will allow you to invoke the handler from JavaScript:

external.run('myhandler').then(function(value) {
    process.return(value);
});

The above will match 'myhandler' with the handler registered as <<"myhandler">>, call run/1 without arguments, fulfill the promise with the value 'hello' and "return" (see below) the value to the calling process.

JavaScript API

The application comes with a few pre-built modules.

process

The process module does cool stuff.

process.return(value)

Return a value to the calling Erlang process. Execution in the current scope proceeds in the VM, but no external events occur after the call to return.

{ok, 1} = erlang_v8_lib:run(<<"process.return(1);">>).

http

Simple HTTP api.

http.request(method, url, [options])

Make a HTTP request to url.

Example:

{ok, _Body} = erlang_v8_lib:run(<<"
http.request('get', 'http://httpbin.org/get')
    .then((resp) => resp.body())
    .then((body) => process.return(body));
});
">>).

Valid options attributes:

• payload: Data to be sent (String)
• headers: Headers to send (Object)

The function returns a promise. The resolve function takes one argument: response. The response object has the following attributes and methods:

• response.json(): Convert payload to a JavaScript structure (Promise).
• response.text(): Return payload as text (Promise).

http.get(url, [options])

Shorthand for http.request('get', url, [options]).

http.post(url, [options])

Shorthand for http.request('post', url, [options]).