capture returned functions in javascript

I have the following piece of code as follows:

function(staticPath) {
    console.log('static Path = ' +staticPath);
    return function(data, response) {

        console.log('data = ' +data);
        console.log('response = ' +response);
        var readStream;
        // Fix so routes to /home and /home.html both work.
        data = data.replace(/^(\/home)(.html)?$/i, '$1.html');
        data = '.' + staticPath + data;
        fs.stat(data, function(error, stats) {
            if (error || stats.isDirectory()) {
                return exports.send404(response);
            }
            readStream = fs.createReadStream(data);
            return readStream.pipe(response);
        });
    }
}

This function basically parses the path to a HTML file and displays the contents of the file.

I am not able to understand how to call this method from outside.

I am calling it as follows:

staticFile("D:\\Node Applications\\public\\home.html")

I can capture it inside a variable innerFunc and i can call the inner function as innerFunc(response) where response is http's serverResponse of which i have the reference with me but i am not sure how can i pass the data param.

I am not understanding what is happening behind the scenes. Can anyone explain ? Do we encounter such kind of code often in javascript ?

EDIT: To make things clear: There is another method as follows:

function(data, response) {
    response.writeHead(200, {
        'Content-Type': 'application/json'
    });
    response.end(JSON.stringify(data));
}

which i call from my node server logic as follows:

http.createServer(function(req, res) {
    // A parsed url to work with in case there are parameters
    var _url;
    // In case the client uses lower case for methods.
    req.method = req.method.toUpperCase();
    console.log(req.method + ' ' + req.url);

    if (req.method !== 'GET') {
        res.writeHead(501, {
            'Content-Type': 'text/plain'
        });
        return res.end(req.method + ' is not implemented by this server.');
    }
    if (_url is something like //localhost:1337/employees) {
            //call employee service which returns *data*.
            // send the data with a 200 status code
            return responder.sendJson(data, res);
        });
    } else {
        // try to send the static file
        /*res.writeHead(200);
        res.end('static file maybe');*/
        console.log('Inside else');
        var staticInner = responder.staticFile("D:\\Node Applications\\public\\home.html");
        staticInner(res);
    }

    // res.end('The current time is ' + Date.now())
}).listen(1337, '127.0.0.1');

As one can see there is no data variable to pass to the innerFunc hence, got confused.