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

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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’.

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