var inside function gets undefined (JavaScript, NodeJS)

Question

I'm having problem with the call of some function, I'm learning JavaScript and NodeJS with the knowledge I get from JavaScript, I don't see the clue why I have this error, the function I'm trying to do is this one:

function isFileView(dat)
{
    var file = dat;

    //Check if im gettint the right data.
    console.log('file is ' + dat);
    var extension = file.lastIndexOf('.') + 1;

    if(extension != 0)
    {
        switch (extension)
        {
            case 'html':
                return file;
                break;

            case 'css':
                return file;
                break;

            case 'js':
                return file;
                break;
        }
    }
    else
    {
        file = file + '.html';
        return file;
    }
}

The dat value returns as undefined and is making my server to stop. I've changed the parameter of the function and the variables inside the function but no clue. This is the whole script I've made so far:

//Load modules
var http = require('http');
var fs = require('fs');
var url = require('url');

//Send message to console.
console.log('starting.');

//Load config JSON file and 
var content = fs.readFileSync("config.json");
var config = JSON.parse(content);
var server_ip = config.server_ip;
var port = config.port;

console.log('Started.');

//Create server.
server = http.createServer(function(request, response)
{
    //if url has GET method.
    if(request.url.lastIndexOf('?') != -1)
    {
        //resolve url only view.
        var view = getUrlView(request.url);

        console.log('requested: ' + view);
        console.log(methodGet(request.url));

        //Get requested page
        fs.readFile('./views' + view + '.html', function(error, data)
        {

            //if error returned, send error message
            if(error)
            {
                response.writeHead(400, {'Content-type': 'text/plain'});
                response.end('Page was not found');
            }

            //if error was not returned, send the html
            else
            {
                response.writeHead(200, {'Content-type': 'text/html'});
                response.end(data);
            }
        });

        if(view == '/')
        {
            response.writeHead(200, {'Content-type': 'text/plain'});
            response.end('Hello world from node.js');
        }
    }

    else
    {
        console.log('requested: ' + request.url);
        isFileView(view);

        //Get requested page
        fs.readFile('./views' + request.url + '.html', function(error, data)
        {

            //if error returned, send error message
            if(error)
            {
                response.writeHead(400, {'Content-type': 'text/plain'});
                response.end('Page was not found');
            }

            //if error was not returned, send the html
            else
            {
                response.writeHead(200, {'Content-type': 'text/html'});
                response.end(data);
            }
        });

        if(request.url == '/')
        {
            response.writeHead(200, {'Content-type': 'text/plain'});
            response.end('Hello world from node.js');
        }
    }

});
server.listen(port);

function getUrlView(dat)
{
    //resolve data.
    var url = dat.lastIndexOf('?');
    url = dat.slice(0, url);

    return url;
}

function methodGet(dat)
{
    //resolve get method (requires url module).
    var url_parts = url.parse(dat, true);
    return url_parts.query;
}

function isFileView(dat)
{
    var file = dat;

    //Check if im gettint the right data.
    console.log('file is ' + dat);
    var extension = file.lastIndexOf('.') + 1;

    if(extension != 0)
    {
        switch (extension)
        {
            case 'html':
                return file;
                break;

            case 'css':
                return file;
                break;

            case 'js':
                return file;
                break;
        }
    }
    else
    {
        file = file + '.html';
        return file;
    }
}

I'm beginner at JavaScript so with NodeJS, but I'm an experienced programmer in PHP so I don't know if the switch works in that way.

Answer 1

The problem appears to be related to how you're defining the view variable which you're passing as an argument to your isFileView() function...

    //if url has GET method.
    if(request.url.lastIndexOf('?') != -1)
    {
        //resolve url only view.
        var view = getUrlView(request.url);

        ....
    }
    else {
        ....
        isFileView(view); // << view isn't defined here since we never were in the 'if` statement above
        ....
    }

So, what you'll need to do is either define the variable before the if statement or inside your else statement or reset your function to check for an undefined argument so it doesn't cause any errors.

else {
    var view = getUrlView(request.url);
    isFileView(view); // << view isn't defined here since we never were in the 'if` statement above
    ....
}

Or...

function isFileView(dat)
{
    var file = dat || false;

    if(file) {
       ...
    }
}