Adding a New Element to an existing JSON Object

Question

i'm trying to add a json object to an existing file in node js: When a members sign up, I want his data to be added to my existing json file. I've found on differents website some tips and code to make it happen but still, it doesnt have any effects.

My Json file look like this right now.

{
  "Family Name": "Vincent",
  "Name": "Test",
  "Promotion": "2A",
  "Mail": "[email protected]",
  "Event": "FE only",
  "Password" : "test"
}

And I want him to look like this when he register :

{
  "Family Name": "Vincent",
  "Name": "Test",
  "Promotion": "2A",
  "Mail": "[email protected]",
  "Event": "FE only",
  "Password" : "test"
},
{
  "Family Name": "Test",
  "Name": "Test",
  "Promotion": "2A",
  "Mail": "[email protected]",
  "Event": "FE only",
  "Password" : "test"
}

Hope you can help me. Thanks a lot !

You need an JSON array at first place. surround the content of the json file with [ ] , then var a = JSON.parse, then a.push(newvalue) then JSON.stringify(a) then save the content in the file. Otherwise you won't end up with a valid json file. — mpm
– mpm, Commented Sep 1, 2018 at 19:19

amrender singh · Accepted Answer · 2018-09-01 19:30:24Z

First of all use a JSON array to maintain your data. You can use the node fs module for reading and updating your file. For Example:

const fs = require('fs');
function readFileAndSaveData(){
   try {
        let userData = fs.readFileSync('user.json');
        userData = JSON.parse(userData);
        userData.push({
          "Family Name": "Test",
           "Name": "Test",
           "Promotion": "2A",
           "Mail": "[email protected]",
           "Event": "FE only",
           "Password" : "test"
        });
        fs.writeFileSync('user.json', JSON.stringify(userData));
    } catch (error) {
        console.log(error);
    }

}

Luca Kiebel · Accepted Answer · 2018-09-01 19:30:21Z

1

You can use some existing libraries (ex: lowdb)

and use it as below

const low = require('lowdb')
const FileSync = require('lowdb/adapters/FileSync')

const adapter = new FileSync('yourfile.json')
const db = low(adapter)
db
  .get('users')
  .push({ "Family Name": "Vincent", "Name": "Test", ... })
  .write()

edited Sep 1, 2018 at 19:30

Luca Kiebel

10.1k7 gold badges34 silver badges47 bronze badges

answered Sep 1, 2018 at 19:27

hovnozrout

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