reason_examples.re

let _ =
  Js.Promise.(
    Fetch.fetch("/api/hellos/1")
    |> then_(Fetch.Response.text)
    |> then_(text => print_endline(text) |> resolve)
  );

let _ =
  Js.Promise.(
    Fetch.fetchWithInit(
      "/api/hello",
      Fetch.RequestInit.make(~method_=Post, ()),
    )
    |> then_(Fetch.Response.text)
    |> then_(text => print_endline(text) |> resolve)
  );

let _ =
  Js.Promise.(
    Fetch.fetch("/api/fruit")
    /* assume server returns `["apple", "banana", "pear", ...]` */
    |> then_(Fetch.Response.json)
    |> then_(json => Js.Json.decodeArray(json) |> resolve)
    |> then_(opt => Belt.Option.getExn(opt) |> resolve)
    |> then_(items =>
         items
         |> Js.Array.map(item =>
              item |> Js.Json.decodeString |> Belt.Option.getExn
            )
         |> resolve
       )
  );

/* makes a post request with the following json payload { hello: "world" } */
let _ = {
  let payload = Js.Dict.empty();
  Js.Dict.set(payload, "hello", Js.Json.string("world"));
  Js.Promise.(
    Fetch.fetchWithInit(
      "/api/hello",
      Fetch.RequestInit.make(
        ~method_=Post,
        ~body=
          Fetch.BodyInit.make(Js.Json.stringify(Js.Json.object_(payload))),
        ~headers=Fetch.HeadersInit.make({"Content-Type": "application/json"}),
        (),
      ),
    )
    |> then_(Fetch.Response.json)
  );
};

let _ = {
  let formData = Fetch.FormData.make();
  Fetch.FormData.appendObject(
    "image0",
    {"type": "image/jpg", "uri": "path/to/it", "name": "image0.jpg"},
    formData,
  );

  Js.Promise.(
    Fetch.fetchWithInit(
      "/api/upload",
      Fetch.RequestInit.make(
        ~method_=Post,
        ~body=Fetch.BodyInit.makeWithFormData(formData),
        ~headers=Fetch.HeadersInit.make({"Accept": "*"}),
        (),
      ),
    )
    |> then_(Fetch.Response.json)
  );
};