This is the comma operator.
The comma operator evaluates both of its operands (from left to right)
and returns the value of the second operand.
The resultant value when a,b,c,...,n is evaluated will always be the
value of the rightmost expression, however all expressions in the
chain are still evaluated (from left to right).
So in your case, the assignations would still be evaluated, but the final value would be bassoon.
Result:
galleons = brigantines
brigantines = bassoon
armada.embrace(basson)
More information: Javascript "tuple" notation: what is its point?
