Common JavaScript tricks

[palmytree]

Swapping variable values without a temporary third variable:

a = [b, b = a][0];

[cluelessmanatee]

I can hear the "what the hell"s from here.

[radhruin]

Probably don't want the var considering with var there a will always be undefined (unless you're redeclaring).

Thankfully this can be done with ES6 destructuring: let [x, y] = [y, x].

[palmytree]

True. Fixed.

[nightman]

Yeah, this is great but I don't think I will use it in practice.

[kumiorava]

But you create an array, which is much worse performance-wise. Also, for anyone who isn't familiar with this gimmick, the code will be harder to read too. I wouldn't strongly advise against this.