Unable to remove data from json file on disk

I’m unable to find a way to remove whole line of JSON data(line) after it’s used. For some reason delete is not working or rather said not doing anything.

.JSON

[
{"id":"1","code":"super-S","expires_in":"","gives_currencies":"1.5","gives_items":"","number_of_attempts":"1","attempts_used":""},
{"id":"2","code":"wow!","expires_in":"","gives_currencies":"3","gives_items":"","number_of_attempts":"1","attempts_used":""},
{"id":"3","code":"slashme","expires_in":"","gives_currencies":"4","gives_items":"","number_of_attempts":"1","attempts_used":""},
{"id":"4","code":"randombla","expires_in":"","gives_currencies":"5","gives_items":"","number_of_attempts":"1","attempts_used":""}
]

code

//fs configuration
const fs = require('fs');
let rawdata = fs.readFileSync('test.json');
let mycodes = JSON.parse(rawdata);

//something above
const randomcode = mycodes[Math.floor(Math.random() * mycodes.length)];
console.log('Your code is:', randomcode['code']); //logs me a random code value
delete mycodes[randomcode];

The goal here is to select random code, which is done but then I need to remove it from .JSON file so it won’t repeat. I tried several things but it’s not working, delete.randomcode etc… the line never removed from the .JSON file.

Answer

Use Array.prototype.splice(index, deleteCount) instead of delete.
delete, on an Array, will just null the key, without removing it.

Save back your modified data using JSON.stringify(mycodes) to that same file.

const fs = require('fs');

const mycodes = JSON.parse(fs.readFileSync('./test.json'));
const randomIndex = Math.floor(Math.random() * mycodes.length);
const randomObject = mycodes[randomIndex];

console.log('Your code is:', randomObject.code); // Log a random code value
mycodes.splice(randomIndex, 1); // Remove one key at randomIndex

// Write back to file
fs.writeFileSync('test.json', JSON.stringify(mycodes, 0, 4), 'utf8');

If you already have that Object out of your Array, and since Objects are passed by reference (like pointer in memory), make use of the Array.prototype.indexOf(someObject) like:

const fs = require('fs');

const mycodes = JSON.parse(fs.readFileSync('./test.json'));
const randomIndex = Math.floor(Math.random() * mycodes.length);
const randomObject = mycodes[randomIndex];

// later in your code....
const objIndex = mycodes.indexOf(randomObject); // Get Object index in Array
mycodes.splice(objIndex, 1); // Remove it from array at that index

// Write back to file
fs.writeFileSync('test.json', JSON.stringify(mycodes, 0, 4), 'utf8');