This post inspired me. I've made some tests.
console.log( false, 5 ); prints false 5 , and it's ok.
console.log( ( false, 5 ) ); prints 5. Now we know that it's ok too because ( false, 5 ) returns 5.
But why does console.log( false, {}, 5 ); print false Object {} 5?
Also console.log( ( false, {}, 5 ) ); and even console.log( ( false, { i:0 }, 5 ) ); both prints 5. Why is 5 is preferred to {}?
You can see here: http://jsfiddle.net/3uUwY/
The comma operator always returns the last element, which is 5.
When using brackets you are forcing Javascript to evaluate that expression.
console.log(a, b, c); // 3 parameters, the function prints a, b and c
console.log((a, b, c)); // 1 parameter. It prints the result of
// evaluating (a, b, c) and, as it's said
// in the other answer, it returns the last element
// of the expression.
By putting brakets you make only one argument to console.log. So following
console.log( false, 5 ); // here you are using log function with 2 argumetns
And here
console.log( ( false, { i:0 }, 5 ) ); // here is only one argument.
Inside a brakets you are using comma operator.
And the comma operator always returns last expression.
So you could rewrite your expression like this:
var x = ( false, { i:0 }, 5 ); // x is 5 here
console.log( x );
i++, j-- is.By putting brakets you make only one argument to console.log. So following
console.log( false, 5 ); // here you are using log function with 2 argumetns
And here
console.log( ( false, { i:0 }, 5 ) ); // here is only one argument.
Inside a brakets you are using comma operator.
And the comma operator always returns last expression.
So you could rewrite your expression like this:
var x = ( false, { i:0 }, 5 ); // x is 5 here
console.log( x );