Add object to JSON with Node.js

Question

I have a JSON file that I need to use as a database to add, remove and modify users, I have this code:

'use strict';

const fs = require('fs');

let student = {  
    id: 15,
    nombre: 'TestNombre', 
    apellido: 'TestApellido',
    email: '[email protected]',
    confirmado: true 
};


let data = JSON.stringify(student, null, 2);
fs.writeFileSync('personas.json', data);

But that overwrites the JSON file, and I need to append as another object, so it continues with id 15 (last one was 14).

Here is a piece of the JSON file:

{
  "personas": [
    {
      "id": 0,
      "nombre": "Aurelia",
      "apellido": "Osborn",
      "email": "[email protected]",
      "confirmado": false
    },
    {
      "id": 1,
      "nombre": "Curry",
      "apellido": "Jefferson",
      "email": "[email protected]",
      "confirmado": true
    },
  ]
}

How can I do this?

Load the file first, keep it in memory and everytime you update that object you also store it back in the file. — MinusFour
– MinusFour, Commented Aug 23, 2018 at 23:30
There are some nice node_modules that can do the fs stuff for you and make it seem like you are just dealing with data. One that comes to mind is lowdb. — Mark
– Mark, Commented Aug 23, 2018 at 23:35
Is this a duplicate? stackoverflow.com/questions/36093042/… — R01010010
– R01010010, Commented Aug 23, 2018 at 23:49

nicholaswmin · Accepted Answer · 2018-08-23 23:54:49Z

2

Just require the file, push the student in the personas prop and writeFileSync it back.

'use strict';

const fs = require('fs');

let current = require('./personas.json');
let student = {
    id: 15,
    nombre: 'TestNombre',
    apellido: 'TestApellido',
    email: '[email protected]',
    confirmado: true
};

current.personas.push(student);

// Make sure you stringify it using 4 spaces of identation
// so it stays human-readable.
fs.writeFileSync('personas.json', JSON.stringify(current, null, 4));

edited Aug 23, 2018 at 23:54

answered Aug 23, 2018 at 23:37

nicholaswmin

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4 Comments

R01010010 Over a year ago

why the sync? just curious

nicholaswmin Over a year ago

To match the OP's preferred method. He/She already uses fs. writeFileSync in the question code snippet.

R01010010 Over a year ago

ah! ok, thought maybe it was really necesary :P

Nachot93 Over a year ago

Thank you! This is exactly what I was looking for!

Antiokus · Accepted Answer · 2018-08-23 23:36:56Z

1

every time you want to write to the JSON file, you’ll need to read it first/parse it, update he Object and then write it to disk.

There’s a popular solution already handling that. Checkout lowdb

For the autoindexing - I believe the documentation suggests ways some helper libraries for this module to make that happen

Don’t reinvent the wheel!

answered Aug 23, 2018 at 23:36

Antiokus

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