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 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

Examples

This Scala code has no meaning but shows basic ideas:

val replacement = "text"
val js = javascript {
  window.setTimeout(() => {
    val r = new RegExp("d.*", inject(replacement))
    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]()
    for (idx <- 0 until list.attributes.length) {
      val attr = list.attributes.item(idx).as[Attribute]
      val text = if (attr.textContent.length > 0) attr.textContent else "default"
      map(attr.name) = func(text)
    }
    val obj = new {
      val field = 1
      def func2(i: Int) = "string"
    }
    val links = Array("https://github.com/nau/jscala", "https://github.com/lampepfl/scala-js")
    for (link <- links) {
      include("var raw = 'JavaScript'")
      console.log(link + obj.func2(obj.field) + point.x)
    }
    window.location.href = links(0).replace("jscala", "jscala/blob/master/README.md")
  }, 1000)
}
println(js.asString)

It will print

window.setTimeout((function () {
    var r = new RegExp("d.*", "text");
    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 = {};
    for (var idx = 0; idx < list.attributes.length; idx++) {
      var attr = list.attributes.item(idx);
      var text;
      if (attr.textContent.length() > 0) {
        text = attr.textContent;
      } else {
        text = "default";
      };
      map[attr.name] = func(text);
    };
    var obj = {
      field: 1,
      func2: (function (i) {
        return "string";
      })
    };
    var links = ["https://github.com/nau/jscala", "https://github.com/lampepfl/scala-js"];
    for (link in links) {
      var raw = 'JavaScript';
      console.log((link + obj.func2(obj.field)) + point.x);
    };
    window.location.href = links[0].replace("jscala", "jscala/blob/master/README.md");
  }), 1000)

How To Use

In your build.sbt add

scalaVersion := "2.10.2"

libraryDependencies += "org.jscala" %% "jscala-macros" % "0.2"

libraryDependencies += "com.yahoo.platform.yui" % "yuicompressor" % "2.4.7"

If you want to try the latest snapshot:

scalaVersion := "2.10.2"

resolvers += Resolver.sonatypeRepo("snapshots")

libraryDependencies += "org.jscala" %% "jscala-macros" % "0.3-SNAPSHOT"

libraryDependencies += "com.yahoo.platform.yui" % "yuicompressor" % "2.4.7"

In your code

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

That's it!

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

• Traits support
• JavaScript frameworks support: jQuery, Angular.js etc
• 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