server.improved.js

const http = require( "http" ),
      fs   = require( "fs" ),
      // IMPORTANT: you must run `npm install` in the directory for this assignment
      // to install the mime library if you"re testing this on your local machine.
      // However, Glitch will install it automatically by looking in your package.json
      // file.
      mime = require( "mime" ),
      dir  = "public/",
      port = 3000

const appdata = [
  { "model": "toyota", "year": 1999, "mpg": 23, age: new Date().getFullYear() - 1999 },
  { "model": "honda", "year": 2004, "mpg": 30, age: new Date().getFullYear() - 2004 },
  { "model": "ford", "year": 1987, "mpg": 14, age: new Date().getFullYear() - 1987 } 
]

const server = http.createServer( function( request,response ) {
  if( request.method === "GET" ) {
    handleGet( request, response )    
  }else if( request.method === "POST" ){
    handlePost( request, response ) 
  }
})

const handleGet = function( request, response ) { 

  if( request.url === "/" ) {
    sendFile( response, "public/index.html" )
  } else if (request.url === "/data") {
    response.writeHead(200, { "Content-Type": "application/json" });
    response.end(JSON.stringify(appdata));
  } else {
    const filename = dir + request.url.slice(1);
    sendFile(response, filename);
  }
  };

const handlePost = function( request, response ) {
  let dataString = ""

  request.on( "data", function( data ) {
      dataString += data 
  })

  request.on( "end", function() {
    const received = JSON.parse(dataString) 

    if (request.url === "/add") {
      received.age = new Date().getFullYear() - received.year
      appdata.push(received)
    } else if (request.url === "/delete") {
      appdata = appdata.filter((_, idx) => idx !== received.index);
    }


    response.writeHead( 200, "OK", {"Content-Type": "application/json" })
    response.end(JSON.stringify(appdata))
  })
}

const sendFile = function( response, filename ) {
   const type = mime.getType( filename ) 

   fs.readFile( filename, function( err, content ) {

     // if the error = null, then we"ve loaded the file successfully
     if( err === null ) {

       // status code: https://httpstatuses.com
       response.writeHeader( 200, { "Content-Type": type })
       response.end( content )

     }else{

       // file not found, error code 404
       response.writeHeader( 404 )
       response.end( "404 Error: File Not Found" )

     }
   })
}

server.listen( process.env.PORT || port )
console.log( "Server listening on port " + ( process.env.PORT || port ) )