Creating .json file and storing data in it with JavaScript?

Question

I have a back-end JavaScript file that runs on node.js. It do some stuff using async.series and yields the final dictionary(object) with data I need on my front-end. I now how to read a .json file and convert it into the JavaScript object, but I do not know create .json file with back-end JavaScript and how to store some data in it.

Could anyone please tell me the right way to do this.

Here is the dictionary(object) that I need to convert and store to the .json file.

var dict = {"one" : [15, 4.5],
            "two" : [34, 3.3],
            "three" : [67, 5.0],
            "four" : [32, 4.1]};

score 33 · Accepted Answer · edited Jul 25 '17 at 19:20

33

Simple! You can convert it to a JSON (as a string).

var dictstring = JSON.stringify(dict);

To save a file in NodeJS:

var fs = require('fs');
fs.writeFile("thing.json", dictstring);

Also, objects in javascript use colons, not equals:

var dict = {"one" : [15, 4.5],
        "two" : [34, 3.3],
        "three" : [67, 5.0],
        "four" : [32, 4.1]};

edited Jul 25 '17 at 19:20

BWP

380
1
17

answered Aug 31 '14 at 09:08

DevilishDB

595
6
12

ok, but how can I create `.json` file and store this `string` into it? – Michael Aug 31 '14 at 09:09
Check the answer now, should be ok – DevilishDB Aug 31 '14 at 09:14
1

tnx but fs.writeFile(...) requires a third (or fourth) parameter which is a callback function to be invoked when the operation completes. – TechDogLover OR kiaNasirzadeh May 24 '19 at 11:47
@ashkannasirzadeh this is right. I just edited this answer so it can work fine. – dzof31 Jul 05 '19 at 09:27

score 15 · Answer 2 · answered May 24 '19 at 11:47

15

1- make your obj:

var dict = {"one" : [15, 4.5],
    "two" : [34, 3.3],
    "three" : [67, 5.0],
    "four" : [32, 4.1]};

2- make it JSON:

var dictstring = JSON.stringify(dict);

3- save your json file and dont forget that fs.writeFile(...) requires a third (or fourth) parameter which is a callback function to be invoked when the operation completes.

var fs = require('fs');
fs.writeFile("thing.json", dictstring, function(err, result) {
    if(err) console.log('error', err);
});

answered May 24 '19 at 11:47

TechDogLover OR kiaNasirzadeh

4,566
27
33

But then how do you generate a json file output – Ae Leung Sep 16 '22 at 07:10
Thanks for adding this answer, I was getting invalid callback error. probably an old version of fs worked without the callback – Rstar37 Mar 07 '23 at 15:33

Creating .json file and storing data in it with JavaScript?

2 Answers2

Linked