fileForm.js

const formidable = require('formidable'), fs = require('fs'), http = require('http')

http.createServer((req, resp	) => {
  switch (req.method) {
   case 'GET':  pideFichero(req,resp); break;
   case 'POST': procesaFichero(req,resp); break;
  }}).listen(3000);

function procesaFichero(req,resp) {
 var form = new formidable.IncomingForm();
 form.parse(req, function(err, fields, files) {
   resp.writeHead(200, {'content-type': 'application/json'});
   fs.readFile(files.fichero.path,'utf8', (err,datos) => {
  	  if (err) throw err;
   	  let json = JSON.parse(datos)
   	  resp.end(JSON.stringify(json));
 })});
 return;
}

function pideFichero(req,resp) {  
  resp.writeHead(200, {'content-type': 'text/html'});
  resp.end('<h1>Cargar fichero JSON</h1>' +
    '<form action="/" enctype="multipart/form-data" method="post">'+
    '<input type="file" name="fichero"><br>'+
    '<input type="submit" value="Enviar">'+
    '</form>'
  );
}