How can i create an array as a database with JSON files and use Javascript to update / save it

Question

I am making a discord bot in Node.js mostly for fun to get better at coding and i want the bot to push a string into an array and update the array file permanently.

I have been using separate .js files for my arrays such as this;

module.exports = [
  "Map: Battlefield",
  "Map: Final Destination",
  "Map: Pokemon Stadium II",
];

and then calling them in my main file. Now i tried using .push() and it will add the desired string but only that one time.

What is the best solution to have an array i can update & save the inputs? apparently JSON files are good for this.

Thanks, Carl

Answer 1

congratulations on the idea of writing a bot in order to get some coding practice. I bet you will succeed with it!

I suggest you try to split your problem into small chunks, so it is going to be easier to reason about it.

Step1 - storing

I agree with you in using JSON files as data storage. For an app that is intended to be a "training gym" is more than enough and you have all the time in the world to start looking into databases like Postgres, MySQL or Mongo later on.

A JSON file to store a list of values may look like that:

{
  "values": [
    "Map: Battlefield",
    "Map: Final Destination",
    "Map: Pokemon Stadium II"
  ]
}

when you save this piece of code into list1.json you have your first data file.

Step2 - reading

Reading a JSON file in NodeJS is easy:

const list1 = require('./path-to/list1.json');
console.log(list.values);

This will load the entire content of the file in memory when your app starts. You can also look into more sophisticated ways to read files using the file system API.

Step3 - writing

Looks like you know your ways around in-memory array modifications using APIs like push() or maybe splice().

Once you have fixed the memory representation you need to persist the change into your file. You basically have to write it down in JSON format.

Option n.1: you can use the Node's file system API:

// https://stackoverflow.com/questions/2496710/writing-files-in-node-js
const fs = require('fs');

const filePath = './path-to/list1.json';
const fileContent = JSON.stringify(list1);

fs.writeFile(filePath, fileContent, function(err) {
  if(err) {
    return console.log(err);
  }

  console.log("The file was saved!");
}); 

Option n.2: you can use fs-extra which is an extension over the basic API:

const fs = require('fs-extra');

const filePath = './path-to/list1.json';

fs.writeJson(filePath, list1, function(err) {
  if(err) {
    return console.log(err);
  }

  console.log("The file was saved!");
});

In both cases list1 comes from the previous steps, and it is where you did modify the array in memory.

Be careful of asynchronous code:

Both the writing examples use non-blocking asynchronous API calls - the link points to a decent article.

For simplicity sake, you can first start by using the synchronous APIs which is basically:

fs.writeFileSync
fs.writeJsonSync

You can find all the details into the links above.

Have fun with bot coding!