JScala

Scala macro that produces JavaScript from Scala code. Let it be type safe!

Supported Features:

Variable definitions, basic unary and binary operations
Named and anonymous functions
Scala Arrays/Seq as JavaScript Array literals
Scala Map and anonymous classes as JavaScript object
if, while, for..in and for statements
Scala if as an expression (e.g. val a = if (true) 1 else 2)
Scala match as JavaScript switch
Basic Scala class/trait definition to JavaScript object definition translation
Global JavaScript functions (parseInt etc)
Basic Browser objects (window, history, location etc)
Basic HTML DOM objects (Document, Element, Attribute, Node, NodeList etc)
Raw JavaScript inclusion
Values and function call injections from your Scala code
Generated JavaScript eval using Java ScriptEngine
Pretty printing and compression using YUI compressor
Basic @Javascript macro annotation support
Basic toJson/fromJson macros
@Typescripted annotation

Examples

This Scala code has no meaning but shows basic ideas:

val replacement = "text"
val js = javascript {
  window.setTimeout(() => {
    val r = new RegExp("d.*", "g")
    class Point(val x: Int, val y: Int)
    val point = new Point(1, 2)
    def func(i: String) = r.exec(i)
    val list = document.getElementById("myList2")
    val map = collection.mutable.Map[String, String]()
    if (typeof(map) == "string") {
      for (idx <- 0 until list.attributes.length) {
        val attr = list.attributes.item(idx).asInstanceOf[Attribute]
        map(attr.name) = func(attr.textContent).as[String]
      }
    } else {
      val obj = new {
        val field = 1
        def func2(i: Int) = "string"
      }
      val links = Array("https://github.com/nau/scala")
      for (link <- links) {
        include("var raw = 'JavaScript'")
        console.log(link + obj.func2(obj.field) + point.x)
      }
      window.location.href = links(0).replace("scala", "jscala")
    }
  }, 1000)
}
println(js.asString)

It will print

window.setTimeout(function () {
    var r = new RegExp("d.*", "g");
    function Point(x, y) {
      this.x = x;
      this.y = y;
    };
    var point = new Point(1, 2);
    function func(i) {
      return r.exec(i);
    };
    var list = document.getElementById("myList2");
    var map = {};
    if (typeof(map) == "string") for (var idx = 0; idx < list.attributes.length; ++idx) {
      var attr = list.attributes.item(idx);
      map[attr.name] = func(attr.textContent);
    } else {
      var obj = {
        field: 1,
        func2: function (i) {
          return "string";
        }
      };
      var links = ["https://github.com/nau/scala"];
      for (var linkIdx = 0, link = links[linkIdx]; linkIdx < links.length; link = links[++linkIdx]) {
        var raw = 'JavaScript';
        console.log((link + obj.func2(obj.field)) + point.x);
      };
      window.location.href = links[0].replace("scala", "jscala");
    };
  }, 1000)

How To Use

In your build.sbt add

scalaVersion := "2.13.2"

libraryDependencies += "org.jscala" %% "jscala-macros" % "0.5"

If you want to try the latest snapshot:

scalaVersion := "2.13.2"

resolvers += Resolver.sonatypeRepo("snapshots")

libraryDependencies += "org.jscala" %% "jscala-macros" % "0.6-SNAPSHOT"

In your code

import org.jscala._
val js = javascript { ... }
println(js.asString)
println(js.compress)
println(js.eval())

That's it!

How To Try Macro Annotations

In your build.sbt add

scalaVersion := "2.13.2"

libraryDependencies += "org.jscala" %% "jscala-macros" % "0.5"

libraryDependencies += "org.jscala" %% "jscala-annots" % "0.5"

In your code

import org.jscala._
@Javascript class User(val name: String, val id: Int)
@Javascript(json = false) class Greeter {
  def hello(u: User) {
    print("Hello, " + u.name + "\n")
  }
}
// Run on JVM
val u1 = new User("Alex", 1)
val greeter = new Greeter()
greeter.hello(u1) // prints "Hello, Alex"
val json = u1.js.json.asString
val main = javascript {
    val u = new User("nau", 2)
    val u1Json = eval("(" + inject(json) + ")").as[User] // read User from json string generated above
    val t = new Greeter()
    t.hello(u)
    t.hello(u1Json)
  }
val js = User.jscala.javascript ++ Greeter.jscala.javascript ++ main // join classes definitions with main code
js.eval() // run using Rhino
println(js.asString) // prints resulting JavaScript

Run it and you'll get

Hello, Alex

Hello, nau
Hello, Alex
{
  function User(name, id) {
    this.name = name;
    this.id = id;
  };
  function Greeter() {
    this.hello = function (u) {
      print(("Hello, " + u.name) + "\n");
    };
  };
  var u = new User("nau", 2);
  var u1Json = eval(("(" + "{\n  \"name\": \"Alex\",\n  \"id\": 1\n}") + ")");
  var t = new Greeter();
  t.hello(u);
  t.hello(u1Json);
}

See AES example:

https://github.com/nau/jscala/blob/master/jscala-examples/src/main/scala/org/jscalaexample/AES.scala

It's AES Scala implementation which is used for both Scala and JavaScript encryption/decryption.

How To Build And Play Some Tetris

Make sure you have at least -Xmx750Mb for your sbt. Don't know why but it takes up to 700Mb to compile jscala-macros project.

In sbt shell run tetris task. It will compile and generate tetris.js file in jscala-examples/javascript-tetris and open Tetris game in your browser. Tetris is fully written in Scala and translates to JavaScript mostly literally.

Tetris sources are here: jscala-examples/src/main/scala/org/jscalaexample/Tetris.scala

Planned Features

Language support improvements
Web frameworks support: Play, Lift

Feedback

Any feedback is very welcome!

You can use JScala mailing list if you have any questions.

Or simply ask me on Twitter: @atlanter

nau / jscala 0.4