How to write/update new JSON file with nodejs

Question

I have some JSON files containing an array of objects. I would like to know how to change one of this object and so change the JSON file (overwriting the old file). I know I can't do that with AngularJS, but with NodeJS on the server-side. This is what I'm trying to do:

---Animazione.json---

[
   {
      "Locandina":"immagini/locandine/A1.jpg",
      "Titolo":"Alla ricerca di Dory",
      "Regista":"Andrew Stanton, Angus MacLane",
      "Eta":"Film per tutti",
      "Durata":"93 minuti",
      "Formato":"DVD",
      "Data":"18 gen. 2017",
      "Prezzo":"14,14€",
      "Quantita":"10"
   },
   ...

---index.html--- (call to the function doPost();)

<td><input id="clickMe" type="button" value="clickme" ng-click="doPost();" /></td>

---app.js---

App.controller('AnimazioneController', ['$scope','$http', function($scope, $http) {

                    $http.get('Animazione.json').success(function(response)
                    {
                        $scope.myData=response;
                    })
                    .error(function()
                    { 
                        alert("Si è verificato un errore!"); 
                    });

                    /*Quantita'*/
                    var dataobj =
                                {
                                    'Locandina':$scope.Locandina,
                                    'Titolo':$scope.Titolo,
                                    'Regista':$scope.Regista,
                                    'Eta':$scope.Eta,
                                    'Durata':$scope.Durata,
                                    'Formato':$scope.Formato,
                                    'Data':$scope.Data,
                                    'Prezzo':$scope.Prezzo,
                                    'Quantita':$scope.Quantita
                                };

                    $scope.doPost = function()
                    {

                      $http.post(dataobj + '/resource', {param1: 1, param2: 2});
                    };


}]);

---index.js-- (Server)

//In server (NodeJS)
var fs = require('fs'); //File system module

server.post('/resource', function(request, response)
{ //Every HTTP post to baseUrl/resource will end up here
    console.info('Updated myJSON.json');
    fs.writeFile('myJSON.json', request.body, function(err)
    {
        if (err)
        {
            console.error(err);
            return response.status(500).json(err); //Let the client know something went wrong
        }
        console.info('Updated myJSON.json');
        response.send(); //Let the client know everything's good.
    });
});

As you can see I tried to write the array of objects in a new JSON file with no results.

What am I doing wrong?

I don't think we need your complete code. In fact, you should probably edit the question and remove code, leaving only the relevant bits. As of "no results", could you elaborate on that? Do you mean that console calls do not even run? — Álvaro González
– Álvaro González, Commented Mar 8, 2017 at 12:32

Taieb · Accepted Answer · 2017-03-08 12:48:43Z

0

fs.writeFileSync(Animazione, JSON.stringify(content));

edit:

Because fs.writefile is a traditional asynchronous callback - you need to follow the promise spec and return a new promise wrapping it with a resolve and rejection handler like so:

  return new Promise(function(resolve, reject) {
    fs.writeFile("<filename.type>", data, '<file-encoding>', function(err) {
        if (err) reject(err);
        else resolve(data);
    });    
});

So in your code you would use it like so right after your call to .then()

.then(function(results) {
    return new Promise(function(resolve, reject) {
            fs.writeFile(ASIN + '.json', JSON.stringify(results), function(err) {
               if (err) reject(err);
               else resolve(data);
            });
    });
  }).then(function(results) {
       console.log("results here: " + results)
  }).catch(function(err) {
       console.log("error here: " + err);
  });

edited Mar 8, 2017 at 12:48

answered Mar 8, 2017 at 12:39

Taieb

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1 Comment

Sangharsh Over a year ago

Why write Synchronously?

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