JavaScript usually automatically converts values to the type that a method or operator needs, which can lead to a variety of bugs. As a counter-measure, Brian McKenna (@puffnfresh) suggests using the following code for your tests:

    Object.prototype.valueOf = function () {
        throw new Error('Use an explicit toString');
    };

Quick tip (via David Klassen): The following shell command lists all (highly experimental!) ECMAScript Harmony [1] features that can be switched on in Node.js.

    node --v8-options | grep harmony

Most people know that ECMAScript is the language standard behind JavaScript [1]. Fewer people know that its name comes from Ecma International, the organization managing this standard. Interestingly, that organization started as “European Computer Manufacturers Association (ECMA)”, but renamed itself to “Ecma International” in 1994. That was done to reflect its increasingly international focus. Ecma is now not considered an acronym, any more. Ecma International is located in Geneva. In contrast, TC39 [1], the Ecma-hosted committee evolving ECMAScript, is rather USA-centric (true to where JavaScript was created and who created it) and usually meets somewhere in California.

2013-12-23: A new blog post on ParallelJS (as Parallel JS is now called) supersedes this post.

Parallel JS will soon be included in Firefox Nightly builds. This project was initially called River Trail [1]. It automatically parallelizes code that uses the ParallelArray type and its array-like methods (map() etc.). [Source of this post: “Parallel JS lands” by Nicholas D. Matsakis.]

TC39 [1] is the committe that currently plans ECMAScript 6 (code-named ECMAScript.next), the next version of the JavaScript language standard. January 29–31, they had another meeting. Thanks to Rick Waldron’s notes, we can read up on what has been decided. This blog post describes the highlights. Previous blog posts summarized prior meetings.

(Note: a blog post on the March TC39 meeting will be posted at some time in the future.)

[Update 2015-02-15] Newer version of this blog post: “Classes in ECMAScript 6 (final semantics)”

In JavaScript, it is difficult to create sub-constructors of built-in constructors such as Array. This blog post explains the problem and possible solutions – including one that will probably be chosen by ECMAScript 6. The post is based on Allen Wirfs-Brock’s slides from a presentation he held on January 29, during a TC39 meeting.

This blog post explores the Lehmer code, a way of mapping integers to permutations. It can be used to compute a random permutation (by computing a random integer and mapping it to a permutation) and more.

This blog post is a quick reminder of how try-finally works.

When it comes to platforms for implementing applications, the term “web platform” seems to increasingly replace “HTML5” (which itself has largely replaced “Ajax” [1]). In this context, both terms denote the programming platform of web browsers. The former includes JavaScript. The latter doesn’t, strictly speaking, but it includes JavaScript-based APIs.

This blog post gives a brief introduction to destructuring in ECMAScript 6 and how the array method forEach() profits from it.