javascript - What are the benefits of a closure, and when are they typically used?

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I'm a web developer, but lots of folks
are looking for slightly more advanced skills and understanding closures seems to be at
the forefront of this.

I get the whole
"execution context creating a reference to a variable that doesnt ever get destroyed"
thing, but really, is this some sort of private or static variable implementation in
JavaScript?

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class="normal">Answer

They can
be good for lots of things, for example, visibility (like private members in traditional
OO).

var count = function(num)
            {

 return function(add) {
 add = add || 1;
 num
            += add;
 return num;

            }


}

href="http://jsbin.com/onuya3/edit" rel="nofollow noreferrer">See
it.

My
count() can be seeded with a number. When I assign a variable
to the return, I can call it with an optional number to add to the internal
num (an argument originally, but still part of the scope of the
returned function).

href="http://www.javascriptkit.com/javatutors/closures.shtml" rel="nofollow
noreferrer">This is a pretty good
overview.

See also on