AliSawari

// A simple BlockChain example via Nodejs
// this example shows the core functionality of a BlockChain system and how it works
// want to add  more options? here's the GitHub rep: https://github.com/AliSawari/SimpleBlockChain
// THIS EXAMPLE IS INSPIRED BY : youtu.be/zVqczFZr124 

// requiring Hash function
const {createHmac} = require('crypto');

// simplify some functions
function str(val){

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var http = require("http");
var fs = require("fs");
var server = http.createServer().listen(3000);

server.on("request", function(req, res) {
  if (req.method != "POST") return res.end();
  var imageName = "received-" + Date.now() + ".jpg";
  var writeStream = fs.createWriteStream(imageName);

  req.pipe(writeStream);

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const axios = require('axios')

...

const requestBody = {
  name: 'Akexorcist',
  age: '28',
  position: 'Android Developer',
  description: 'birthdate=25-12-1989&favourite=coding%20coding%20and%20coding&company=Nextzy%20Technologies&website=http://www.akexorcist.com/',
  awesome: true

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// including the net module
const net = require('net');

// clients array
let clients = [];

// a nice little logger with a time stamp
// loggin messages for both server and Client
function logger(m){
  let d = new Date().toLocaleString();

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// ok

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// with each return , the value goes for the next then in chain
// you can chain as many thens as you want, even if you dont return a value

doSomething(args).then(result => {
  return result + 2
}).then(plusTwo => {
  return plusTwo + 2
}).then(plusFour => {
  // and the chain continues as many thens as you want...
}).catch(err => console.log(err))

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// say take a number and return its double

// resolve : the success call . which goes in the first then
// reject : the error call, which goes in .catch

function double(number){
  return new Promise((resolve, reject) => {
    if(typeof number == 'number'){
      resolve(number * 2)
    } else reject("the argument should a Number")

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function double(number, callback){
  if(number > 2){
    callback(null, number * 2)
  } else {
    callback(new Error("number should be more than 2"))
  }
}

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// import it!
const { promisify } = require("util")

// turn your ordinary func into a promise func!
const doublePromise = promisify(double)

// use it! 
doublePromise(14).then(res => {
  console.log(res)
}).catch(err => console.log(err))

AliSawari

const { readFile } = require('fs')
const { promisify } = require('util')

const readFilePromise = promisify(readFile)

readFilePromise('myFile').then(data => {
  console.log(data.toString())
}).catch(e => console.log(e))