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Brackets and semicolon after function definition

I recently saw a function in someone else's code that looked like this:

function xyz(){ //function code here ;
} ();

I don't understand ();

after defining the function.

Can someone tell me what a value is ();

and when to use it in JavaScript?

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1 answer


The code you are showing does not compile.

With the parentheses added, this would be a named immediately called function:

(function xyz(){ //function code here ;
}) ();

Most often, these functions are anonymous:



(function(){
   var a; // a isn't visible outside
   // code using a
})();

The code is directly called, as with no function definition, but the point of such a function is to define a scope (which can only be a global scope or a function) so that the scope variable does not flow into the attached one. This pattern is very useful for keeping your code clean: you don't add any variable to the outer scope, and you cannot remove an existing one.

Here, the function also has a name that can be used internally for recursion.

(function xyz(){
   var a; // a isn't visible outside
   // code using a and calling xyz
})();
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