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 variables, like this:

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

This works, but the square brackets seem completely superfluous.

Is there a purpose of using this syntax or is it technically incorrect, but ignored by the browser?

Answer 1

Just in case anyone else arrives here while trying to find out what some weird/new syntax involving [square brackets] (seen in someone else's Javascript) might possibly be, like I was...

Nowadays, with ES6, we also have [] used on the left-hand side for destructuring arrays, e.g.

const names = ['Luke', 'Eva', 'Phil'];  const [first] = names;   console.log(first); // 'Luke'  const [first, second] = names;   console.log(first, second); // 'Luke' 'Eva' 

For further info see http://www.deadcoderising.com/2017-03-28-es6-destructuring-an-elegant-way-of-extracting-data-from-arrays-and-objects-in-javascript/ or google 'es6 destructuring'.