Develop Reference

How do I use node.js on a localhost:8000 server?

I have some pure JS code and HTML and CSS on my localhost:8000 server. I have installed node.js and I am able to use it without problem testing it on the VS code terminal. However, I want to integrate the file reading mechanic of node.js into the code that I am running on the localhost:8000 server. I want to put this node.js code into my webpage on localhost:8000
const {readFileSync, promises: fsPromises} = require('fs');
function syncReadFile(filename) {
const contents = readFileSync(filename, 'utf-8');
const arr = contents.split(/\r?\n/);
console.log(arr); // 👉️ ['One', 'Two', 'Three', 'Four']
return arr;
}
syncReadFile('./locations.txt');
I have tried copy and pasting it into the js file for the webpage, however when I run it, the console says
Uncaught ReferenceError: require is not defined
at window.onload (index.js:23:46)
index.js:23:46 is the line where const {readFileSync, promises: fsPromises} = require('fs'); is.
How do I fix this?

I think you need a better understanding of how NodeJS works:
Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine.
A JavaScript runtime is (in this context) a program that runs in a machine, with tools to interact with that machine. In development, the context of that machine is the context of a Server.
Now, JavaScript found it's use in the HTML script tag, that's the most "vanilla" way to execute JS in it's home, what it's most used for. In this context, JavaScript is running as a Client.
What makes NodeJS, different from executing the same code in an HTML file you can already execute without installing NodeJS?
It's as vanilla as you can get after you "force" JavaScript to be executed in the Backend, but for it to be used as a webserver, there are some tools that need to be ported, converted or even created, some of these tools, like the File System (fs) are specific to NodeJS.
That's it! TLDR is that your code won't work because it's being executed in the wrong place. You can fix that in many ways, like this one, but maybe you can find a better path understanding how NodeJS works

Browsers cannot access file systems like that. Nodefs will not work within the browser

The NodeJS modules only works on the server side, you can't use it client side (that also include the require() syntax).
If you want to read a file from the server, you might want to use an AJAX directed to the route that has a controller to read the targeted file, which then the result of the AJAX is handled client side with vanilla JS.

Javascript to read Text File to Array without a Webserver or external libraries local on Windows PC

I have an HTML file with JavaScript that I am running without any Webserver/host so I am just opening the file in a browser local to my windows PC. In that HTML file I would like to be able to read a text file in the same folder as the html file. That file will contain data in rows and columns separated with tabs. i.e
1 a
2 b
3 c
I want to keep this as simple as possible so all I have to do is share the HTML and Text file to others so the can open it up local to their computer without any webserver/host and without having to also copy of external libraries like node.js or jquery.
I have searched and tested everything I can find but either I need to reference an external library or I have to run it in a webserver or I need to click a button to load the file through the browser, none of what I want.
Does native JavaScript support the function to read a text file and save it to an array? If so, any code direction would be great.

https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest
XMLHttpRequest() exists in native JavaScript, I think it will help you.
You also can send a request to the file. Or use library: axios.js because when you use XMLHttpRequest() you lose many time to write code which just get content from file, with axios I got file content with one line: `axios.get('file.txt').then(result => console.log(result.data));
To connect Axios: <script src="https://unpkg.com/axios#0.18.0/dist/axios.min.js"></script>
You can read official documentation about axios.js and XMLHttpRequest() in the net.

WebAssembly/emscripten: write files to disk from within browser

I have some C code I would like to execute in a Browser (testing with Firefox 64.0). The C code writes a file to disk.
I have been trying to use the emscripten's File System API for many many hours now and I am getting nowhere.
I have read this relevant question and the emscripten doc states the same:
if your C/C++ code does use files, then file system support will be automatically included.
Here is my test code which uses the file system:
#include <stdio.h>
#include <stdlib.h>
int main() {
FILE *f = fopen("testfile.txt", "w");
if (f == NULL) {
printf("Error opening file!\n");
exit(1);
}
const char *text = "This is my test string";
int i = 1234;
fprintf(f, "Some text: %s; and an int: %d\n", text, i);
fclose(f);
printf("End of file.\n");
}
After I compiled this code with:
emcc test.c -o test.html
And opening it with Firefox, I initially expected the file to be saved onto my machine. (I have no JS background.)
I am now almost certain that it does not work like that.
The file is accessible as Uint8Array via:
var array = FS.readfile("testfile.txt")
in the console.
Specifically, I am now interested in this:
Is there a way to write a file to my local filesystem from inside the browser?
Can I download the created file in some way?
Thank you for your time.

TLDR; Never expect you could write anything in your machine on a browser.
Modern web browsers are designed with security in mind so they are highly sandboxed. They are never going to allow web pages to write/open a local file in your machine. Imagine someone visit your website and then a file called testfile.txt is created in their machine, and the website keeps creating files every time you press the refresh button.
WebAssembly has no exception. It is just a virtual machine to run code written in languages other than Javascript. Keep in mind that WebAssembly is run by a JavaScript engine. So saying "I have no JS background." is simply an invalid statement. What JS can't do is what WebAssembly can't.
According to the Emscripten File System Overview documentation, the files you create will stay in the memory. You have to convert it to Blob (this has to be done using JavaScript API) to allow users to download.

c++ tiny-js execute javascript function from external file

I have a C++ application which has to execute a Javascript-function from a dynamic file. (I need to read a proxy.pac file).
E.g. I have a C++ application running which reads the following file: proxy.pac (which contains the javascript function FindProxyForURL(url, host), which I have to call with the two parameters.
However, I have no idea how to start off and I can't find anything on the internet so far.
So basically my question is: how doe I load dynamic Javascript from a file and execute a function within that code(/file)

I made application server using TinyJS.
see this.
https://github.com/pochi0701/wizdlive

Passing Value from C++ to Javascript

i have a c++ file which reads values from a sensor and I want to display those values on a website dynamically. So Im looking for a way to pass these values(integers) from my cpp file to an javascript which displays them on the site.
My first, simple try was to write the values into a js file as variables every second from my cpp script. The Js then uses this file as a source and displays its variables on the site:
cpp:
fprintf(file, "var mx=%d, my=%d, mz=%d, ax=%d, ay=%d, az=%d, gx=%d, gy=%d, gz=%d;\n",
imu.raw_m[0], imu.raw_m[1], imu.raw_m[2], // M = Magnetometer
imu.raw_a[0], imu.raw_a[1], imu.raw_a[2], // A = Accelerometer
imu.raw_g[0], imu.raw_g[1], imu.raw_g[2] // G = Gyroscope
);
html/js:
<script src="./imu.js" type="text/javascript"></script>
The Problem now is of course, that I need to refresh the page all the time, because the imu.js file is cached by the website.
I'd rather have a way to directly pass to integers from the cpp file to the js script. I read something about json or Googles V8 script. But I'd like to hear your suggestions first.
By the way, Im running this on a raspi, if this is important.
Thanks for your help
EDIT:
I'm goning to try it with a mysql database, in which my cpp file writes the data from the sensor with Connector/c++ from http://dev.mysql.com/doc/connector-cpp/en/ and my website reads them.

You could compile your C++ code into a Node.js plugin, you can then register a JavaScript function with your plugin which the C++ calls when it updates the value. That way you can pass values directly from C++ into Javascript in a managed and controlled way.
Node.js has the added benefit of being able to host your webpage and do all the Websocket and HTTP stuff that can be a pain in C++.

You do not have to refresh if your script is smart about how to access the data file! In case you do have a webserver at hand: Take care that your data file is accessible by your webserver and then let your script request the file via ajax (link to w3schools)

I'm doing something similar on a BeagleBone Black. With websocketd you can turn pretty much any program into a websocket endpoint and then send data via stdin and stdout commands. This would be a particularly good solution for you since websockets are designed to handle information that's constantly changing.