Adding a new key value inside a JSON file using NodeJS

Question

Here is what I'm trying to do in my Javascript File:

const file = require('../../data/files.json');
var data = {
  "wolf": {"nani": "awoo"},
  "loli": {"nani": "kimochi"}
}

file.push(data);

My current .json file contents:

{
  "cat" : {
    "nani": "meow"
  },
  "dog": {
    "nani": "woof"
  }
}

Here's kind of what I want my .json file to be after writing to the JSON file using NodeJS:

{
  "cat" : {
    "nani": "meow"
  },
  "dog": {
     "nani": "woof"
  },
  "wolf": {
    "nani": "awoo"
  },
  "loli": {
    "nani": "kimochi"
  }
}

Is this possible? If so thank you~!

Klaycon · Accepted Answer · 2020-01-03 17:35:21Z

2

Yes, of course it's possible to modify JSON at runtime. However there are three problems with your current approach.

file.push(data) - .push() is a function on Arrays. However, file is not an array, it is an object. You can use something like Object.assign(file, data) to assign all the properties from data to file instead.
Your data is in a different format than how you want your JSON result to look like. Instead of "wolf": "awoo" it needs to be "wolf": { "nani": "awoo" }, for example. You could keep it in the current format but you'd have to transform the data to get it in the right result format.
Modifying the JSON this way only modifies the copy of the JSON held in memory when it's read by require(). You still need to save this modified copy of the JSON. Just like in a text editor where your changes aren't saved until you hit the save button. To do this you can use fs.writeFile and JSON.stringify:
```
//import the standard filesystem module to read/write files and folders
const fs = require("fs"); 

//after you modify your data use this to save the changes
fs.writeFile("../../data/files.json", JSON.stringify(file), err => {
    if(err) console.log(err);
});
```

JSON.stringify is needed because const file = require(...); will convert the JSON to a JavaScript object. JSON is just text, a JS object is an in-memory data structure that has a prototype and properties and such things. JSON.stringify converts it back to text so you can just save the text version of the object.

Unrelated to your question, but I see you're using discord.js, so this is probably for a discord bot. If you plan on modifying this JSON with a command, be wary that if your bot gets added to many servers, JSON storage gets very unstable and is likely in the future to lose/corrupt the data. This can happen for many reasons, but it's because every time you change the data it requires a full rewrite of the file, and if the process fails during the rewrite it is left in a corrupted state.

I strongly recommend using a proper database solution to store dynamic data, like postgres, redis, or any other SQL/NoSQL solution.

edited Jan 3, 2020 at 17:35

answered Jan 3, 2020 at 17:10

Klaycon

11.1k23 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Yazuki Rin Over a year ago

Hi~ I received the following error: UnhandledPromiseRejectionWarning: TypeError [ERR_INVALID_CALLBACK]: Callback must be a function. Received undefined

Klaycon Over a year ago

@YazukiRin I've edited the answer with a callback for writeFile. A recent version of node must have required it.

Yazuki Rin Over a year ago

Thanks a lot! It worked perfectly! Also thanks for the suggestion! I'm using SQLite for my Discord Bot's Database~! You've been a great help! :D

Klaycon Over a year ago

@YazukiRin That is a good choice. I'm glad the answer was useful for you. :)

Praveen Patel · Accepted Answer · 2020-01-03 17:10:34Z

1

You can try like this

let file = require('../../data/files.json');
console.log(file);

// to add key value pair in any Object use like this :-
// object['key'] = 'value'
file['wolf'] = {
    "nani": "awoo"
}
file['loli'] = {
    "nani": "kimochi"
}
console.log(file);

answered Jan 3, 2020 at 17:10

Praveen Patel

3477 silver badges26 bronze badges

1 Comment

Yazuki Rin Over a year ago

I kind of meant to write it into the .json file, sorry if I made you misunderstand :(

engelant · Accepted Answer · 2020-01-03 17:10:34Z

0

You would have to read in the content of the file, add your changes and write out the file again.

What you did would result in this:

{
  "cat" : {
    "nani": "meow"
  },
  "dog": {
    "nani": "woof"
  }
}
{
  "wolf": {
    "nani": "awoo"
  },
  "loli": {
    "nani": "kimochi"
  }
}

You can't just append to JSON, you need to modify it. And to modify it you need to parse it.

answered Jan 3, 2020 at 17:10

engelant

14310 bronze badges

Collectives™ on Stack Overflow

Adding a new key value inside a JSON file using NodeJS

3 Answers 3

4 Comments

1 Comment

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

1 Comment

Comments

Related