How to write array to a file properly on node.js express with fs?

Question

I'm trying to write an array as its on the file with node.js and i've used angular to achive this, you can inspect rest of the code from this question.

When i send an array, file seems like this: [object Object],...

When i send my array inside JSON.stringify(myArr), it writes properly on the file but data corrupts and converts as an a object.

json:

[{
  "name"    : "BigTitleLine1",
  "content" : "APP TITLE 1"
}, {
  "name"    : "BigTitleLine2",
  "content" : "APP TITLE 2"
}];

node.js:

var express     = require('express'),
    fs          = require('fs'),
    bodyParser  = require('body-parser'),
    app         = express();

app.use(express.static(__dirname));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

app.put('/update', function (req, res) {

  console.log(req.body);
  fs.writeFile("./json/test.json", req.body, function(err) {
    res.json({ success: true });
  });
  // this returns true data on console 
  // but it writes [object Object],[object Object] to the file

  var jsonData = JSON.stringify(req.body);
  console.log(jsonData);
  fs.writeFile("./json/test.json", jsonData, function(err) {
    res.json({ success: true });
  });
  // this way writes well but
  // it corrupts data and convert it to object:
  //{"0":{"name":"BigTitleLine1","content":"APP TITLE 1"},"1":{"name":...}}
});

var server = app.listen(3000);

I'm trying to write array as its on the file.

Stringifying your data should work. Have you tried removing the first fs.writeFile, i.e. only trying it with the second fs.writeFile (where you're stringifying your payload). Because now you have two async write statements that are creating a race condition that could potentially cause weird stuff to happen. — danillouz
– danillouz, Commented Aug 28, 2015 at 12:54
thanks for the help @danillouz but i didn't understand, can you write it down :? — Barlas Apaydin
– Barlas Apaydin, Commented Aug 28, 2015 at 12:55

zag2art · Accepted Answer · 2015-08-28 13:25:49Z

4

This should work fine:

var express     = require('express'),
    fs          = require('fs'),
    bodyParser  = require('body-parser'),
    app         = express();

app.use(express.static(__dirname));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

app.put('/update', function (req, res) {
  // convert object to array
  var arr = []
  for (var index in req.body){
    arr.push(req.body[index])
  }
  var jsonData = JSON.stringify(arr, null, 2);
  console.log(jsonData);
  fs.writeFile("./json/test.json", jsonData, function(err) {
    res.json({ success: true });
  });
});

var server = app.listen(3000);

edited Aug 28, 2015 at 13:25

answered Aug 28, 2015 at 13:04

zag2art

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5 Comments

danillouz Over a year ago

Am I missing something? Why do you require the loop?

Barlas Apaydin Over a year ago

hello mate, its because node.js thinks my model is an object but it should think as an array @danillouz

danillouz Over a year ago

Oh I think I get it now, it's because of the angular model (array like object). Cool, thanks @BarlasApaydin, you have a badass website btw :)

Barlas Apaydin Over a year ago

hi mate, i've one more question, how can i compress this output and remove whitespaces from json array which you create ?

zag2art Over a year ago

change JSON.stringify(arr, null, 2); to JSON.stringify(arr);

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