What do square brackets around an expression mean, e.g. `var x = a + [b]`?

Question

We have received some JavaScript from an agency that looks wrong, but works.

For some reason they are adding square brackets ([, ]) around v

Answer 1

It's possible to construct a situation where this:

var some_variable = 'to=' + other_variable;

and this:

var some_variable = 'to=' + [other_variable];

produce different results. Specifically, if the Array.prototype.toString() method (or, I suppose, the Array.prototype.join() method) has been changed from its default, anything could happen. For example, extra functionality could be added to the Array.prototype.toString() method to generate logging information, do some lookups, or anything really.

The likelihood that this has been done is slim, I'd imagine, but it needs to be mentioned for completeness.