Unexpected JavaScript...

[SlightlyLoony]

Every once in a while, I run across something completely unexpected in JavaScript. This morning was one of those times.

In my code, I had the equivalent of this:

var x = 0;
if ('' == x)
    gs.log('What the???');
else
    gs.log('Ah, that was expected!');

Wanna take a guess which statement was logged?

In JavaScript, an empty string evaluates as equal to a zero. Doesn't make any sense to me, but apparently it made sense to a JavaScript designer. I suspect what's going on here is that the empty string is coerced to a number (which would be zero) and is then compared to the number 0 in variable x. What I expected was the opposite: that the number 0 would be coerced to the string '0', and the comparison would have evaluated to a false.

I fixed the code like this:

var x = 0;
if ('' == '' + x)
    gs.log('What the???');
else
    gs.log('Ah, that was expected!');

This forces the coercion to happen as I expected (and wanted) it to.

Another day, another oddity!