Reason script to traverse a native JSON object

json_to_string.re

type json = Js.Json.t;

let x: json = [%bs.raw {|{"a": [1, "hello", 2, {"b": {"c": [100,200, "d", [10,20,30]]}}]}|}];

let rec json_to_string json => {
  let array_to_string a => a |> Array.to_list |> String.concat ",";
  let emitObject o =>
    "{" ^
    {
      let emitKV (key, value) => key ^ ": " ^ json_to_string value;
      let dict = Js.Dict.entries o;
      array_to_string (Array.map emitKV dict)
    } ^ "}";
  let emitArray a => "[" ^ array_to_string (Array.map json_to_string a) ^ "]";
  switch (Js.Json.classify json) {
  | JSONNull => "null"
  | JSONTrue => "true"
  | JSONFalse => "false"
  | JSONNumber n => string_of_float n
  | JSONString s => "\"" ^ s ^ "\""
  | JSONArray a => emitArray a
  | JSONObject o => emitObject o
  }
};

Js.log (json_to_string x);