rescript-express

(nearly) zero-cost bindings to express

Installation

Run the following in your console:

$ yarn add rescript-express express

Then add rescript-express to your bsconfig.json's bs-dependencies:

 {
   "bs-dependencies": [
+    "rescript-express"
   ]
 }

Module system

For now, due to compability issues between commonJS and ES6 module, the bindings expose two express functions:

• express for ES6
• expressCjs to CommonJS

Be careful to pick the right one given your compiler's configuration.

API

The API closely matches the express one. You can refer to the express docs.

Notable differences

• express.json, express.raw, express.text, express.urlencoded, express.static are all suffixed with Middleware to prevent name clashing.
• accept* and is return an option intead of a string/boolean
• req.get is called getRequestHeader and res.get is called getResponseHeader

You can check the interface file to see the exposed APIs.

Example

open Express

let app = express()

app->use(jsonMiddleware())

app->get("/", (_req, res) => {
  let _ = res->status(200)->json({"ok": true})
})

app->post("/ping", (req, res) => {
  let body = req->body
  let _ = switch body["name"]->Js.Nullable.toOption {
  | Some(name) => res->status(200)->json({"message": `Hello ${name}`})
  | None => res->status(400)->json({"error": `Missing name`})
  }
})

app->useWithError((err, _req, res, _next) => {
  Js.Console.error(err)
  let _ = res->status(500)->endWithData("An error occured")
})

let port = 8081
let _ = app->listenWithCallback(port, _ => {
  Js.Console.log(`Listening on http://localhost:${port->Belt.Int.toString}`)
})

Generates the following

var Express = require("express");

var app = Express();

app.use(Express.json());

app.get("/", function (_req, res) {
  res.status(200).json({
    ok: true,
  });
});

app.post("/ping", function (req, res) {
  var body = req.body;
  var name = body.name;
  if (name == null) {
    res.status(400).json({
      error: "Missing name",
    });
  } else {
    res.status(200).json({
      message: "Hello " + name,
    });
  }
});

app.use(function (err, _req, res, _next) {
  console.error(err);
  res.status(500).end("An error occured");
});

app.listen(8081, function (param) {
  console.log("Listening on http://localhost:" + String(8081));
});