how to create JSON string in Erlang manually

Question

I am new to Erlang and noticed that there is no native function to create json string from lists (Or is there?). I use this method to create json string in Erlang but do not know if it will not malfunction.

Here is an example of my method:

-module(index).
-export([test/0]).

test() ->
    Ma = "Hello World", Mb = "Hello Erlang",
    A = "{\"Messages\" : [\"" ++ Ma ++ "\", \""++Mb++"\"], \"Usernames\" : [\"Username1\", \"Username2\"]}",
    A.

The result is:

388> test().
"{\"Messages\" : [\"Hello World\", \"Hello Erlang\"], \"Usernames\" : [\"Username1\", \"Username2\"]}"
389> 

I think this is the expected result but is there any chance that this method may malfunction when included special characters, such as: <, >, & / \ " ??

What precautions should I take to make this method stronger?

Answer 1

If Ma or Mb contains double quotes or whatever control characters, the parsing from string to JSON will fail. This parsing may never occur in Erlang, as Erlang does not have string to JSON conversion built-in.

It's a good idea to use binaries (<<"I am a binary string">>), as lists consume a lot more resources.

We're using jiffy, which is implemented as a NIF and hence is reasonably fast and it allows for document construction like so:

jiffy:decode(<<"{\"foo\": \"bar\"}">>).
{[{<<"foo">>,<<"bar">>}]}
Doc = {[{foo, [<<"bing">>, 2.3, true]}]}.
{[{foo,[<<"bing">>,2.3,true]}]}
jiffy:encode(Doc).
<<"{\"foo\":[\"bing\",2.3,true]}">>