Sometimes I see JavaScript that is written with an argument provided that already has a set value or is an object with methods. Take this jQuery example for instance:

$(.selector).children().each(function(i) {

    console.log(i);

});

When logging i, you would get the value of whatever i is in that iteration when looking at the selectors children in the jQuery each method.

Take this Node.js example:

http.createServer(function(request, response) {

    response.writeHead(200, {Content-Type: text/plain});

    response.write(Hello World);

    response.end();

}).listen(8888);

You can see here that request and response are being passed and they contain their own methods that can be acted on.

To me, this looks like were passing a function to the createServer function with two arguments that have methods already attached to them.

My question is a multipart one:

1. Where do these arguments come from?


2. If these are just anon functions, how do they receive arguments that can be acted on like other functions?


3. How do I create functions that can take my own arguments like this??


4. Does this use the power of closures??