Hi there,
it might sound silly but out of curiosity I just created a test case for
this one using a snippet of code to test both declarations performance.
There seems to be no difference in that respect, have a look:
http://jsperf.com/testing-parens
Fran
On 15/02/11 09:12, Peter van der Zee wrote:
On Tue, Feb 15, 2011 at 9:53 AM, Ivan S <[email protected]
<mailto:[email protected]>> wrote:
Hi all.
I don't know ECMA script specification so well, so if someone can
explain what's the difference between this two:
(function() {
}());
(function() {
})();
(brackets have different positioning)
Intuitively, I can understand the difference, but I would like
technical explanation.
The parenthesis are actually a "grouping operator" in js. In practice
this means that you can change the order of precedence for operators
using parens, `5+(7*9)` vs `(5+7)*8`. We do it all the time, most of
the time without even thinking about it.
Specification-wise, the grouping operator combined with the comma
operator can have some minor effects, especially with eval and other
edge cases. This is due to the (specification) internal notion of a
Reference. I'm sure somebody will jump on this ship to explain that in
detail if you're interested ;)
As for the given example, there is absolutely no difference, a
function is created first and executed right after doing so. There are
no observable differences. Internally, the difference is whether the
grouping operator returns a function or the result of calling that
function.
- peter
Thank you very much.
Ivan
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