Is there a difference between (function() {…}()); and (function() {…})();? [duplicate]

Possible Duplicate:
Location of parenthesis for auto-executing anonymous JavaScript functions?

Sometimes I see:

(function() { ... }()); 

and sometimes I see:

(function() { ... })(); 

I see both forms with and without arguments. They both execute the anonymous function.

Is there a difference between the two forms? Are there any compelling reasons to use one form over the other?



There is no practical difference in those two forms, but from a grammatical point of view the difference between the two is that The Grouping Operator - the parentheses - will hold in the first example a CallExpression, that includes the FunctionExpression:

                |         |
       FunctionExpression |
                |         |
                V         V
    (function() {       }());
    ^                      ^
    |--PrimaryExpression --|

In the second example, we have first a whole CallExpression, that holds the FunctionExpression:

    (function() {       })();
    ^                      ^
    |--  CallExpression  --|


As far as differences go, it is really just syntactic sugar. Somewhat equivalent to: "do you like jQuery() or $()?" Both can be compiled, executed, and used interchangeably (AFAIK).

From the code samples I have seen thus far, more people seem to follow the Crockford code convention:

(function() { ... }()); 

Personally, I prefer the (function(){})(); convention because it is more apparent to me that the function is self-executing; I'm also a big user of jQuery and that's the convention used in jQuery source.

Additionally, it is considered good practice to use parens to enclose your self-executing function, regardless of which form you choose to go with.


There is no difference between the two, so far as the compiler is concerned. However, will find that the (function () {}()) style is recommended in Douglas Crockford’s JavaScript code conventions.


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