Indirect function call in JavaScript

There are things like

f.call(...)
f.apply(...)

But then there's this

(1, alert)('Zomg what is this????!!!11')

"1" does not seem to mean much in this context, the following works just fine:

(null, alert)('Zomg what is this????!!!11')
(1, null, alert)('Zomg what is this????!!!11')
(undefined, alert)('Zomg what is this????!!!11')

Could you point to a specific part of ECMAScript which describes that syntax?