Optional Parameters in Javascript

Want a nice laugh? Here it comes.

For years, I've been hacking in JavaScript, as it were, "on the side". Just as a necessary, sometimes fun, often loathesome part of the webproject experience.

When doing optional parameters, I always did this:

function foo(a) {
    if (arguments.length === 2)
        b = arguments[1];
    else
        b = 'bar';
}

The problem with this is so obvious I won't even spell it out.

Here's the puncher.

What I somehow managed to miss until today, is that you can also do this:

function foo(a, b) {
    if (typeof(b) === 'undefined')
        b = 'bar';
}

Shorter, sweeter, more obvious. If I'd just known this a bit earlier.