NodeJS (current & LTS)

This is a complete Scala.js facade for Node.js and npm packages; which means you can develop full-blown Node.js applications using popular JavaScript software stacks including the MEAN Stack (MongoDB, Express, Angular, Node), Cassandra, MySQL and many other popular npm packages.

Table of Contents

• Introduction
• Development
  • Build Requirements
  • Building the SDK
  • Resolvers
  • Developed using ScalaJs.io
  • Discussions
  • Advantages over JavaScript
• Node.js bindings
  • Modules
  • Third-party Modules
  • Integration Guidance
• Express.js bindings
• MongoDB bindings
• Angular.js bindings
  • Scala.js Refinements
  • Social Network bindings

Introduction

The goal of this project is to provide a complete Scala.js binding for the entire MEAN Stack. Why? Because I love NodeJS, but I have a love/hate relationship with JavaScript. And many others feel the same way about JavaScript, which is why there are so many languages that are designed to improve the experience (CoffeeScript, TypeScript, Scala.js and others). Simply put, ScalaJs.io let's me have my cake and eat it too! And as such, I've gone to great lengths to bring all the things you love about developing applications on the MEAN Stack to Scala.

ScalaJs.io is a componentized platform; allowing developers to use only the features they want. If all your application requires is a binding for AngularJS, you can use just that. Alternatively, you could use only the Node bindings, or the entire MEAN stack (or any of the bundled npm library bindings).

Currently, there are at least four development use cases for ScalaJs.io:

• Building full MEAN stack applications using the bundled MongoDB, Express, Angular and Node bindings.
• Building rich thin-client web front-ends using AngularJS bindings only (with any backend).
• Building REST services using Node (and optionally Express) bindings only.
• Building CLI applications using Node bindings only.

Development

Build Requirements

• [SBT 0.13.16] (http://www.scala-sbt.org/download.html)

Build/publish the SDK

 $ sbt clean publish-local

Resolvers

To add the ScalaJs.io bindings/library to your project, add the following to your build.sbt:

resolvers += Resolver.sonatypeRepo("releases") 

Developed using ScalaJs.io

The following applications were developed using ScalaJs.io:

The MEAN Stack — AngularJS, MongoDB, Mongoose, Express and more

Looking for a complete list of available bindings? Go here

Discussions

There's a discussion about ScalaJs.io on Reddit.

Advantages over JavaScript

Scala.js offers many advantages over native JavaScript:

• Scala.js is strongly-typed
• Excellent IDE support
• No JavaScript Warts
• More concise
• Go beyond JavaScript ES6, today

Consider the following example in JavaScript. Here we have a nested collection of callbacks (read: pyramid of doom) in order to gather the information that we display at the end.

JavaScript and Node.js

var output1 = null;
var output2 = null;
var output3 = null;

fs.mkdirp("/a/test/dir", function (err1) {
    Assert.ifError(err1);

    fs.writeFile("/a/test/dir/file.txt", "Hello World", function (err2) {
        Assert.ifError(err2);

        fs.readFile("/a/test/dir/file.txt", function (err3, data) {
            Assert.ifError(err3);
            output1 = data; // ~> Buffer("Hello World")

            fs.unlink("/a/test/dir/file.txt", function (err4) {
                Assert.ifError(err4);

                fs.readdir("/a/test", function (err5, dir) {
                    Assert.ifError(err5);
                    output2 = dir; // ~> ["dir"]

                    fs.stat("/a/test/dir", function (err6, stats) {
                        Assert.ifError(err6);
                        output3 = stats.isDirectory(); // ~> true

                        fs.rmdir("/a/test/dir", function (err7) {
                            Assert.ifError(err7);
                            fs.mkdirp("C:\\use\\windows\\style\\paths", function (err8) {
                                Assert.ifError(err8);

                                console.log("output1 =", output1.toString(), output1);
                                console.log("output2 =", output2);
                                console.log("output3 =", output3)
                            })
                        })
                    })
                })
            })
        })
    })
});

Now consider the equivalent logic in Scala.js using its much more elegant for comprehension:

Scala.js and Node.js

import io.scalajs.nodejs.console
import io.scalajs.nodejs.Fs._

for {
  _ <- Fs.mkdirpFuture("/a/test/dir")
  _ <- Fs.writeFileFuture("/a/test/dir/file.txt", "Hello World")
  output1 <- Fs.readFileFuture("/a/test/dir/file.txt") // ~> Buffer("Hello World")
  _ <- Fs.unlinkFuture("/a/test/dir/file.txt")
  output2 <- Fs.readdirFuture("/a/test") // ~> ["dir"]
  output3 <- Fs.statFuture("/a/test/dir").map(_.isDirectory()) // ~> true
  _ <- Fs.rmdirFuture("/a/test/dir")
  _ <- Fs.mkdirpFuture("C:\\use\\windows\\style\\paths")
} {
  console.log("output1 =", output1.toString(), output1)
  console.log("output2 =", output2)
  console.log("output3 =", output3)
}

Node.js

The Node.js integration is nearly complete (feature for feature), and should be more than sufficient for most web-based and CLI applications. Additionally, there are a growing number of third-party (mostly OSS) modules that have been implemented as well, including bcrypt, cassandra-driver, kafka-node, mysql, xml2js and many others.

var http = require("http");
http.createServer(function(request, response) {
    response.writeHead(200, {"Content-Type": "text/plain"});
    response.write("Hello World");
    response.end();
}).listen(8888);

import io.scalajs.nodejs.http._
import scalajs.js

Http.createServer((request: ClientRequest, response: ServerResponse) => {
    response.writeHead(200, js.Dictionary("Content-Type" -> "text/plain"))
    response.write("Hello World")
    response.end()
}).listen(8888)

Express.js

The following is a simple Hello World app in Node and Express using JavaScript:

var express = require('express');
var app = express();

app.get('/', function (req, res) {
   res.send('Hello World');
})

var server = app.listen(8081, function () {
  var host = server.address().address
  var port = server.address().port
  console.log("Example app listening at http://%s:%s", host, port)
})

Here's the same example using Scala.js:

import io.scalajs.nodejs.console
import io.scalajs.npm.express._

val app = Express()

app.get("/", (req: Request, res: Response) => res.send("Hello World"))

val server = app.listen(8081, connect)

private def connect: js.Function = () => {
    val host = server.address().address
    val port = server.address().port
    console.log("Example app listening at http://%s:%s", host, port)
}

The following is a more elaborate example:

import io.scalajs.npm.express._
import io.scalajs.util.ScalaJsHelpers._
import scalajs.js

val todos: js.Array[Todo] = emptyArray

val app = Express()

app.use(BodyParser.json())
app.use(BodyParser.urlencoded(new UrlEncodedBodyOptions(extended = true)))   

app.get("/api/todo/:id", (request: Request, response: Response) => getTodo(request, response))
app.get("/api/todos", (request: Request, response: Response) => getTodos(request, response))
app.post("/api/todo", (request: Request, response: Response) => createTodo(request, response))

def createTodo(request: Request, response: Response) = {
    request.bodyAs[Todo] match {
        case todo if todo.hasTitle =>
            todo.id = UUID.randomUUID().toString
            todos.push(todo)
            response.send(todos)
        case todo =>
            response.badRequest(todo)
    }
}

def getTodo(request: Request, response: Response) = {
    val todoId = request.params("id")
    todos.indexWhereOpt(_.id == todoId) match {
        case Some(index) => response.send(todos(index))
        case None => response.notFound(todoId)
    }
}

def getTodos(request: Request, response: Response) = response.send(todos)

@js.native
trait Todo extends js.Object {
    var id: String = js.native
    var title: String = js.native
    var completed: Boolean = js.native
}

implicit class TodoExtensions(val todo: Todo) extends AnyVal {

    @inline
    def hasId: Boolean = Option(todo).flatMap(t => Option(t.id)).exists(_.trim.nonEmpty)

    @inline
    def hasTitle: Boolean = Option(todo).flatMap(t => Option(t.title)).exists(_.trim.nonEmpty)

    @inline
    def isComplete: Boolean = hasId && hasTitle

}

MongoDB

The following example demonstrates establishing a connection to MongoDB using Scala.js:

import io.scalajs.nodejs.console
import io.scalajs.npm.mongodb._
import io.scalajs.util.ScalaJsHelper._

// Connection URL. This is where your mongodb server is running.
val url = "mongodb://localhost:27017/test"

// Use connect method to connect to the Server
MongoClient.connect(url, (err, db) => {
    if (isDefined(err)) {
        console.log("Unable to connect to the mongoDB server. Error:", err)
    } else {
        // HURRAY!! We are connected. :)
        console.log("Connection established to: %s", url)

        // TODO do some work here with the database.

        // close connection
        db.close()
    }
})

Or, if you'd like to be more Scala idiomatic, the connection fragment could be written as follows:

import io.scalajs.nodejs.console
import io.scalajs.npm.mongodb._
import scala.util.{Success, Failure}

MongoClient.connectFuture(url) onComplete {
    case Success(db) =>
        // HURRAY!! We are connected. :)
        console.log("Connection established to: %s", url)

        // TODO do some work here with the database.

        // close connection
        db.close()
    case Failure(e) =>
        console.log("Unable to connect to the mongoDB server. Error:", e.getMessage)  
}

Alternatively, you could choose to use "foreach" to directly manage only the success case:

import io.scalajs.npm.mongodb._
import io.scalajs.util.PromiseHelper._

MongoClient.connectFuture(url) foreach { db => 
    // HURRAY!! We are connected. :)
    console.log("Connection established to: %s", url)

    // TODO do some work here with the database.

    // close connection
    db.close()
}

ScalaJs.io exposes Future-based alternatives to most of the asynchronous functions found in MongoDB, Express, Angular and Node. This means that you can use Scala's amazing for comprehensions to replace the dreaded pyramid of doom callbacks normally associated with JavaScript asynchronous code.

Consider the following:

for {
    // List all the virtual machine images you can use.
    vmImages <- computeManagementClient.virtualMachineVMImages.listFuture

    // Create a cloud service.
    computeManagementClient <- computeManagementClient.hostedServices.createFuture(
      HostedServicesOptions(serviceName = serviceName, label = "cloud service 01", location = "West US"))

    // Create a virtual machine in the cloud service
    deployment <- computeManagementClient.virtualMachines.createDeploymentFuture(serviceName, deploymentOptions)
} {
    console.info(deployment)
}