Node.js First steps, don’t know how to start

Question

I’ve been dedicating myself to Javascript for some time, looking for various ways to learn, recently I came across the callback functions, usually used when using javascript on a server instead of local (correct me if I’m wrong).

I found a series of exercises to learn how to simulate a server with Ode, downloaded all the files and now I intend to start programming on it. However the exercises I am following to learn step by step, it is not clear to me yet, follow what is suggested:

What he means in "the server must respond to /file/* URI? And then map to a Folder location. I can’t understand what I should do to start working with this. If someone could give a clearer explanation, so that a beginner could understand and develop something, or even a generic code as an example, it would also be very productive to the studies. Thank you very much.

All I’ve done so far is:

 var http = require('http');

function onrequest(request, response) {
  response.writeHead(200);
  response.end("Hello World\n");
}

var server = http.createServer(onrequest);
server.listen(8000);

console.log("Listening on http://127.0.0.1:8000/");

Answer 1

This onrequest function will be called each time there is a request to the server.

You have two parameters in that function, the first is the object of the request (request) and in it you have a property called url. This means that when the server receives a request it will call this function and pass as argument an object request where you can read the request.url.

For example: if you call console.log(request.url); inside that function and in the browser you put http://localhost:8000/file.text1.js you will see in the terminal the requested url or /file.text1.js.

Then you can put logic to filter the routes you want with Regexp. For example, if the route starts with /file/ go read a file to a specific directory can be done like this:

const http = require("http");
const fs = require("fs");

const rootFolder = __dirname;

function onrequest(request, response) {
  console.log(request.url);
  const isFileFolder = request.url.match(/^\/file\/*/);
  if (isFileFolder) {
    const fileName = request.url.slice(5); // remover "/file"
    const data = fs.readFileSync(rootFolder + fileName, "utf8");
    response.writeHead(200);
    response.end(data);
    return;
  }

  response.writeHead(200);
  response.end("Hello World\n");
}

const server = http.createServer(onrequest);
server.listen(8000);

console.log("Listening on http://127.0.0.1:8000/");

I tested this example that I wrote as follows: I put this code inside a file called server.js and then in the browser called http://localhost:8000/file/server.js. This returned the contents of server.js.

Now you just need to adapt to your specific case and change the value of rootFolder.