how to save to dev enviorment npm code example

Example 1: setup node js express basic setup

npm init -y
npm i express

Example 2: how to use http in development mode for nodejs

var   fs = require("fs"),
      http = require("https");

var privateKey = fs.readFileSync('sslcert/server.key').toString();
var certificate = fs.readFileSync('sslcert/server.crt').toString();

var credentials = {key: privateKey, cert: certificate};

var server = http.createServer(credentials,function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
});

server.listen(8000);