Dmitry,
if you correctly insert the missing semicolons both versions work,
without semicolons both version fail.
Version 1:
var foo = function () {
return "foo";
};
(function () {
return "IIFE";
})();
Version 2:
var foo = function () {
return "foo";
};
(function () {
return "IIFE";
}());
Try them in a console, the correct result is when the "IIFE" string is
printed out.
Without semicolon, "Version 2" will not throw errors but will not
produces the "IIFE" string either.
The problem is that in "Version2" the "IIFE" string just become a
parameter to the self invoking function resulting by omitting the
semicolons.
var foo = function () { return "foo"; }(function () { return "IIFE"; }());
var foo = function () { return "foo"; }("IIFE");
ASI is hard.
--
Diego
On Wed, Feb 16, 2011 at 12:26 PM, Dmitry A. Soshnikov
<[email protected]> wrote:
> The only observable difference is a very specific. It related with ASI
> (automatic semicolon insertion) mechanism. E.g.
>
> Version 1:
>
> var foo = function () {
> return "foo";
> }
>
> (function () {
> return "IIFE";
> })();
>
> Version 2:
>
> var foo = function () {
> return "foo";
> }
>
> (function () {
> return "IIFE";
> }());
>
> The version 1 fails, the second one -- does not. Why? Which changes to
> provide for that version 1 don't fail?
>
> But as mentioned, this case is very specific and just academical. In real
> practice, only the convenience in this case does matter.
>
> (function () {})(); -- here first we get a FE (evaluating the expression
> inside the grouping operator) and the call it.
>
> (function () {}()); -- here we evaluate the grouping operator which directly
> evaluates the function execution.
>
> Additional info:
> http://dmitrysoshnikov.com/ecmascript/chapter-5-functions/#question-about-surrounding-parentheses
>
> Dmitry.
>
>
> On 15.02.2011 11:53, Ivan S 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.
>>
>>
>> Thank you very much.
>>
>>
>>
>> Ivan
>> --
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>
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>
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