Checking whether a value is an integer in JavaScript

Integers lead an odd life in JavaScript. In the ECMAScript specification, they only exist conceptually: All numbers are always floating point and integers are ranges of numbers without decimal fractions (for details, consult “Integers in JavaScript” in “Speaking JavaScript”). In this blog post, I explain how to check whether a value is an integer.


Implementing a raffle in JavaScript

At two recent occasions, there were copies of “Speaking JavaScript” to be raffled off. This blog post describes two ways of drawing winners via JavaScript.


Understanding the four layers of JavaScript OOP

JavaScript OOP is baffling: on one hand, there is a simple core, on the other hand, there are some really weird things going on. I’ve been pondering for a long time how to explain it well and I think the best way to do so is via four layers: single objects, prototype chains, constructors, constructor inheritance. The first two layers are JavaScript’s simple OOP core, layers 3 and 4 are where the complications start.


We’re doing syntax highlighting wrong

James Fisher mentions two things that are often syntax-highlit wrong:

  • Comments in source code: “The comment is washed out. While the rest of the text exists in black, boldface, and bright colors, the comments fade into the background. […] The implication is obvious: we have collectively decided that the comment is less important than the code.”

  • Insertions and deletions in diff viewers: “[…] a red line is one that was deleted, and a green line is one that was added. […] Our diff viewer, then, tells us that deletions are bad, dangerous, and possibly an error, while insertions are good, safe, and successful.”

Consult the blog post for the rationales and several instructive illustrations.


ECMAScript 6’s new array methods

Check out my book (free online): “Exploring ES6”. Updated version of this blog post: chapter “New Array features”.

This blog post explains what new array methods ECMAScript 6 will bring and how to use them in current browsers.

Note: I’m using the terms constructor and class interchangeably.


Meet the site of the Web Components community

The Web Components community has a new site: WebComponents.org. Quoting Addy Osmani:

WebComponents.org is the home for the community to learn and discuss Web Components.

The site had previously been soft-launched at webcomponents.github.io and is now online at the final URL. It’s good to have a single site with a simple URL where one can look up information related to this important technology. The site’s twitter account is @Web_Components.


Identifying the current <script> element

Guest blog post by Rodney Rehm

You may find yourself in a situation requiring you to know the DOM context of the JavaScript that is currently executing. The DOM context of a running JavaScript is the <script> element that caused the JavaScript to be executed in the first place. With HTML5 the WhatWG introduced document.currentScript, which this article will use to explain simple techniques to make use of DOM context.


JavaScript’s “this”: how it works, where it can trip you up

In JavaScript, the special variable this is relatively complicated, because it is available everywhere, not just in object-oriented settings. This blog post explains how this works and where it can cause problems, concluding with best practices.