Node.js server fails to render pages

Hello everyone! I am trying to render two pages in a simple toy application to better understand Node.js and TypeScript. The index page is supposed to display a simple message when going to localhost:3000 or / while the 404 page is supposed to display an error message whenever an invalid URL is entered.

Error Message

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be one of type string, Buffer, or URL. Received type undefined
at Object.open (fs.js:406:10)

Summary

The two issues I am encountering are properly using the fs module's readStream() method and absolute vs relative directory paths.

What I've already tried so far

I've done a lot of Googling and found a lot of StackOverflow posts. The majority that I have read are either relevant to other modules or are using readFile(). The only thing I've taken away from my searches is to use Node's path module for resolving directory / file names.

Additionally, I have tried using console.log() to log my requests to the server and the path that path.join() is reading.

Here is my project structure:

server_html (top level aka root directory)
-- node_modules
-- src
↳ index.ts
-- views
↳ 404.html
↳ index.html
package-lock.json
package.json
prettier.config.json
tsconfig.json
tslint.json

Code Snippets

Here are my imports, status codes, route map, and port:

import * as http from 'http';
import * as fs from 'fs';
import * as path from 'path';

const httpOkStatus: number = 200;
const httpNotFoundStatus: number = 404;

const routeMap: any = {
    "/": path.join(__dirname, "..", "views", "index.html"),
    "/index": path.join(__dirname, "..", "views", "index.html")
};

const port: number = 3000;

Here's the code for my server:

const app: http.Server = http
    .createServer((req: http.IncomingMessage, res: http.ServerResponse) => {

        res.writeHead(httpOkStatus, {
            "Content-Type": "text/html"
        });

        const pathToIndexView: string = routeMap[req.url as string];
        const sendToErrorPage: boolean = !routeMap[req.url as string];

        if (sendToErrorPage) {
            res.writeHead(httpNotFoundStatus, {
                "Content-Type": "text/html"
            });
            let errorPageFileStream: fs.ReadStream = fs.createReadStream(path.join(__dirname, "..", "views", "404.html") as string, "utf8");
            errorPageFileStream.pipe(res);
            res.end();
        }
        const src: fs.ReadStream = fs.createReadStream(pathToIndexView, "utf8");

        src.pipe(res);
        res.end();
    });

app.listen(port);
console.log(`The server has started and is listening on port number: ${port}`);

FYI, my Index View is boilerplate HTML with a simple <h1>Welcome!</h1>.

Since the error is coming from Object.open(fs.js:406:10), my guess is that this error is happening within one of the fs.createReadStream() methods. The questions I have are:

Why is the path to my Error page a type of undefined?

Why is my index page not rendering my message of "Welcome!"?

Here are my logged paths for both my error page and my index page:

Error:  C:\Users\Daniel\Documents\TypeScript\serve_html\views\404.html
Index:  C:\Users\Daniel\Documents\TypeScript\serve_html\views\index.html

Next Steps

1. I am going to go through Node's official API documentation to see what I can learn about the fs, path, and http modules.
2. I may need to dig into the network traffic to see where my requests are going to. I've already looked at some calls in Chrome's Network tab, but I am considering using separate tools to see all data paths.

I'm new to Node.js and would appreciate even glances at this problem. In the meantime, I will keep searching to find answers and / or stumble onto a working version of this.