In ECMAScript 5, you have a few options for ensuring that a required parameter has been provided, all of which are somewhat brittle and inelegant:

    function foo(mustBeProvided) {
        if (arguments.length < 1) throw new Error(...)
        if (! (0 in arguments)) ...
        if (mustBeProvided === undefined) ...
    }

In ECMAScript 6, you can (ab)use default parameter values to achieve more concise code (credit: idea by Allen Wirfs-Brock):

Are you curious how many recursive calls you can make on your JavaScript engine?

I many cases, if you are presenting in front of an audience, you will create slides, visual material of some kind. I’m a very visual person myself and learn much better if I can read in addition to listen. Slides are also helpful when you lose attention for a few seconds.

There are a variety of software technologies out there for helping you with creating slides. Following are ones that I find intriguing:

The <label> element has been around for a while, but I still don’t see enough websites use it. In lets you make labels of checkboxes and radio buttons clickable.

This blog post explains how the index works that Array.prototype.reduce() passes to its callback.

This blog post explains how JavaScript dates are stored internally as time values, milliseconds since 1970-01-01.

According to the ECMAScript specification, all numbers in JavaScript are floating-point. Yet, the notion of integer comes up occasionally. This blog post explains what it means.

On 2012-05-31, I held the talk “Fake operator overloading” at Fluent Conference, in San Francisco. The video is now publicly available (go there for a larger version of the video).