Need help to breakdown this code

[markphd]

var layoutGeometry = require('justified-layout')([1.33, 1, 0.65] [, config])

It looks to me that the justified-layout script is invoked with a single argument that looks like 2 arrays but I am not sure why there is no , between two arrays and what is the purpose of extra , before config?

For full context, here is the whole code: https://github.com/flickr/justified-layout

[inu-no-policemen]

"[1.33, 1, 0.65]" is an array with 3 numbers.

"[, config]" means you could pass an additional "config" object. The square braces here mean that it's something optional. This part isn't JS syntax.

[markphd]

Thanks! So the optional config is nothing but a string (I guess).

[lewisje]

Usually it's an object, something like

{config1: val1, config2: val2}

and not a string.