The ECMAScript 5.1 specification states that the array method concat is generic [1]. This post argues that that isn’t true in practice.

The new Node.js module “lazylines” allows you to read a text stream, one line at a time, lazily.

This post tells you how to generate emails on Node.js and open them in an email program. It uses mailto URLs to do so. The advantage of this approach is that you can manually check and edit such emails before sending them.

openurl is a Node.js module for opening a URL via the operating system. This will usually trigger actions such as:

• http URLs: open the default browser
• mailto URLs: open the default email client
• file URLs: open a window showing the directory (on OS X)

Update 2012-02-24: New content in sections

• 2.1. Function-scoped variables
• 2.2. Inadvertent sharing via a closure
• 2.7. for...in is weird

JavaScript has many pitfalls. This post examines whether they make JavaScript “unfixable” as a language – as some argue. To do so, it separates the pitfalls into two categories: The ones that become harmless after learning about them and the ones that don’t. We’ll also look at how the upcoming ECMAScript 6 fixes most problems.

Warning: If you are new to JavaScript then don’t let this post be your introduction to it. Consult other material first.

In a conversation triggered by Tim Haines, Twitter front end engineer Dan Webb refers to his article “It's About The Hashbangs” on the problems of using #! URLs in JavaScript. He then goes on to confirm:

JavaScript only has floating point numbers. This post explains how integer operations are handled, specifically the bit shift operations. It will also answer the question whether n >>> 0 is a good way of converting a number to a non-negative integer.

The npm module jsdom enables you to use jQuery to examine and transform HTML on Node.js. This post explains how.

Update: New section “Detecting NaN”.

This post looks at two special values that can be the result of operations that normally return numbers: NaN and Infinity.

Tabs were a major usability advancement for web browsers. They make it much easier to work with multiple locations at the same time and the ability to open links “in the background” turns them into a to-do list for pages that one still wants to read. However, before long, tabs also exhibit the negative traits of to-do lists: There are too many things still to consider and everything grows stale. This post presents ideas for how to tame tabs, for how to avoid those traits. Some of the ideas can be put into practice right now, others are about improving browsers and making a mental shift to fully exploit those improvements.