learn nodejS

June 12, 2020

Here is a way to update your node js version to the current stable version or current latest version Get the latest stable version

sudo npm cache clean -f
sudo npm install -g n
sudo n stable

Or you can get the latest and not stable version using

sudo n latest

This changes your current the path of your nodejs and if you’re using the same shell run update the path with

PATH="$PATH"

Or Fix path ny running

sudo apt-get install --reinstall nodejs-legacy     # fix /usr/bin/node

Create a basic server in node js

Make a web server that responds to a http request.

Create a .js file eg.server.js

//A basic node server

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

const server = http.createServer((req, res) => {
res.setHeader('Content-Type', 'text/html');
let path = './views/';

switch(req.url) {
    case '/':
        path += 'index.html';
        res.statusCode = 200;
        break;
    case '/about':
        path += 'about.html';
        res.statusCode = 200;
        break;
    case '/about_me':
        res.statusCode = 301;
        res.setHeader('Location', '/about');
        res.end();
    default:
        path += '404.html';
        res.statusCode = 404;
        break;
}

fs.readFile(path, (err, data) => {
    if(err) {
        console.log(err);
        res.end();
    } else {
        // res.write(data);
        res.end(data);
    }
})
});

server.listen(5000,'localhost', ()=> {
    console.log("Server created");
});

Run the server by running node server.js on the terminal

Using pre and post scripts (NPM)

Here we create and append the content in the .gitignore file when we run the script.

package.json

{
  "name": "demo",
  "version": "1.0.0",
  "description": "npm scripts tips",
  "main": "app.js",
  "scripts": {
    "test": "test",
    "ignore": "echo \"\" > .gitignore",
    "preignore": "touch .gitignore",
    "postignore": "echo \".gitignore\n.vscode\nnode_modules/\" > .gitignore "
  },
  "author": "Davis",
  "license": "ISC"
}

Using debug module

Install debug module.

npm i debug

Set the environment variable.

DEBUG=davis node app.js

const debug = require("debug")("davis");

debug("debugging with debug module")
console.log("hello world");

let array1 = [].fill(123, 0, 10000);

let array2 = array1.map(item => item * 10);

debug("debug after loop");

NPM versioning

{
  "name": "demo",
  "version": "1.0.0",
  "description": "npm scripts tips",
  "main": "app.js",
  "scripts": {
    "test": "test",
    "build": "npm version patch",
    "ignore": "echo \"\" > .gitignore",
    "preignore": "touch .gitignore",
    "postignore": "echo \".gitignore\n.vscode\nnode_modules/\" > .gitignore "
  },
  "author": "Davis",
  "license": "ISC",
  "dependencies": {
    "debug": "^4.3.1"
  }
}

Handling HTTP requests

const http = require('http');
const url = require('url');
const StringDecoder = require('string_decoder').StringDecoder;
const util = require('util');
const formidable = require('formidable');

//create a server with the http module
const server = http.createServer(function(req, res){
    //req.method eg. GET,POST, req.headers
    // console.log(http.METHODS, http.STATUS_CODES)
    let path = url.parse(req.url, true);
    //path.pathname, path.search, path.port, path.protocol, path.origin
   if(req.method.toLowerCase() == 'post') {
    let form = new formidable.IncomingForm();
    form.parse(req, function(err, fields, files){
        if(err){
            console.log(err)
            return;
        }
        res.writeHead(200, "OK", {"Content-Type": "text/plain"});
        res.write("The POST output response\n\n");
        res.end(util.inspect({fields: fields, files:files}));
    })
   }else if(req.method.toLowerCase() == 'get') {
    res.writeHead(200, "OK", {"Content-Type": "text/plain"});
    res.write("The Response");
    res.write(util.inspect(path.query) + "\n\n");
    res.end("End of Response");
   } else {

   }

  
});

//listen to request on port 5000
server.listen(5000, function(){
    console.log("listening on port 5000");
});