Announcing Scala.js 0.6.11

Announcing Scala.js 0.6.11

Jul 27, 2016.

We are pleased to announce the release of Scala.js 0.6.11!

This release was mainly focused on optimizations. In particular, Longs have been dramatically improved, with up to 15x speedups (#1488). Some operations on BigIntegers benefit a lot from this, with up to 8x speedups.

We have also finally upgraded the version of the Google Closure Compiler that is used for fullOptJS, which brings speed improvements to the production applications of up to 2x, although mostly in the 10-15% range (#2490).

Getting started

If you are new to Scala.js, head over to the tutorial.

Release notes

If upgrading from 0.6.5 or earlier, please also read the release notes of 0.6.6, which contains some breaking changes.

As a minor release, 0.6.11 is backward source and binary compatible with previous releases in the 0.6.x series. Libraries compiled with earlier versions can be used with 0.6.11 without change. 0.6.11 is also forward binary compatible with 0.6.8 through 0.6.10, but not with earlier releases: libraries compiled with 0.6.11 cannot be used by projects using 0.6.{0-7}.

Please report any issues on GitHub.

Potentially breaking change

This release fixes #2445, which potentially constitutes a breaking change, if you relied on the previously buggy behavior. Recall that, in JavaScript types and exports, defs without parentheses are JavaScript getters. For example,

class Foo extends js.Object {
  def makeArray: js.Array[Int] = js.native

val foo = new Foo
val a = foo.makeArray // in JavaScript, this is foo.makeArray, *not* foo.makeArray()

The bug #2445 was that, if makeArray was defined with type parameters, it would erroneously translate to a method call in JavaScript, rather than a field access/getter call.

class Foo extends js.Object {
  def makeArray[A]: js.Array[A] = js.native

val foo = new Foo
val a = foo.makeArray[Int] // gave foo.makeArray() because of #2445

Now that #2445 is fixed, the last instruction correctly calls foo.makeArray without parentheses.

If you were relying on the previously buggy behavior (i.e., it was correct in your case to have foo.makeArray()), your code will break in this release. The solution in that case is to add () at the definition site of makeArray, like this:

def makeArray[A](): js.Array[A] = js.native

Deprecating @JSExportNamed

The annotation @JSExportNamed was deprecated, per #2442. Refer to its Scaladoc for migration tips.

Improvements to the HTML test runners

In 0.6.10, we introduced HTML test runners. This release brings a few improvements to them:

  • #2476 The outputs are grouped by test suite, in collapsible boxes
  • #2481 Failed tests are moved to the top of the UI
  • #2475 It is possible to filter the set of tests to run, for a quicker turnaround when debugging a few issues

Clean way to find the .map file associated to fastOptJS/fullOptJS

Previously, to find the source map file (.map) associated to the .js file produced by fastOptJS or fullOptJS, it was necessary to compute it by hand, by adding .map to the file name. This was not very clean.

We have improved this in #2494. Now, you can access the source map file to an attribute of the result of fastOptJS and fullOptJS. For example,

val fastOptAttrFile = fastOptJS.value
val fastOptFile = // the .js file
val fastOptSourceMapFile = fastOptAttrFile.get(scalaJSSourceMap).get // the .map file


  • #2507 java.util.Optional
  • #2533 java.util.EventObject

Bug fixes

Among others, the following bugs have been fixed:

  • #2471 The BufferedReader implementation does not close its underlying Reader
  • #2474 2+ top-level exports with the same name cause trouble at run-time
  • #2491 Name clash in some cases after renaming by the Closure Compiler in fullOpt
  • #2512 java.util.Arrays.asList() cannot be called
  • #2513 @JSExport does not work for abstract vals and vars
  • #2539 java.util.ConcurrentHashMap.putIfAbsent() is wrong
  • #2445 Paren-free def’s with type-parameters are handled as a function in js.native traits

You can find the full list on GitHub.