Announcing Scala.js 0.6.31

Nov 21, 2019.

We are pleased to announce the release of Scala.js 0.6.31!

This release upgrades the version of the Scala standard library to 2.12.10 and 2.13.1. The upgrade to 2.13.1 notably fixed a number of issues. The release also contains the definitions for BigInt and its typed arrays BigInt64Array and BigUint64Array, thanks to @exoego, as well as the implementation of java.util.IdentityHashMap, thanks to @ekrich.

If you are wondering where v0.6.30 went, it was severely broken and hence was never announced.

Read on for more details.

Getting started

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

Release notes

If you use .scala build files in project/ and are upgrading from Scala.js 0.6.22 or earlier, do read the release notes of 0.6.23, which contain a source breaking change in that situation.

If upgrading from Scala.js 0.6.14 or earlier, make sure to read the release notes of 0.6.15, which contain important migration information.

As a minor release, 0.6.31 is backward binary compatible with previous releases in the 0.6.x series. Libraries compiled with earlier versions can be used with 0.6.31 without change. 0.6.31 is also forward binary compatible with 0.6.29, but not with earlier releases: libraries compiled with 0.6.31 cannot be used by projects using 0.6.{0-28} (nor from the broken 0.6.30).

Please report any issues on GitHub.

Add js.BigInt and its typed arrays

BigInts have made it to Stage 4 of the ECMAScript language evolution process, which means that they are now standard, and will be part of ECMAScript 2020. @exoego contributed type definitions in the Scala.js standard library to be able to manipulate them. As a simple example:

import scala.scalajs.js

def fact(n: js.BigInt): js.BigInt =
  if (n == js.BigInt(0)) js.BigInt(1)
  else n * fact(n - js.BigInt(1))

// prints: 265252859812191058636308480000000

Successfully running this program will require a recent version of Node.js.

The definitions for BigInt64Array and BigUint64Array are also available, in the package scala.scalajs.js.typedarray.



The class java.util.IdentityHashMap is now available, thanks to a contribution by @ekrich.

Add js.special.strictEquals to perform JavaScript’s ===

You can now use js.special.strictEquals(x, y) to perform exactly the same operation as JavaScript’s x === y, known as strict equality. In Scala.js 0.6.x, x eq y is equivalent, but in Scala.js 1.x, x eq y will be stricter to better match Scala/JVM: it will consider +0 and -0 as different, but NaN equal to itself.

Using js.special.strictEquals should be rare. Usually eq does the right thing.

Bug fixes

Among others, the following bugs have been fixed in 0.6.31:

  • #3865 Scala.js 0.6.30 does not acknowledge IR version 0.6.29 as supported.
  • #3778 Using ListBuffer.clone() breaks Vector with Scala 2.13
  • #3808 Seq.unapplySeq(LazyList.from(0)).drop(1) causes infinite loop (upstream bug fixed in 2.13.1)
  • #3848 FunctionEmitter incorrectly classifies ArraySelect as side-effect free

You can find the full list on GitHub for issues fixed in 0.6.30 and issues fixed in 0.6.31.