Working With JSON in JavaScript

json_tests.js

import { readFile, writeFile } from 'fs/promises';
import { readFileSync, writeFileSync } from 'fs';
function writeToJson(path, data, rewrite = false) {
    let old_data = readFileSync(path);
    if (old_data.length == 0 || rewrite == true) {
        writeFileSync(path, JSON.stringify(data, null, 4));
        return;
    }
    let json_obj = [JSON.parse(old_data)]; // without brackets it reverts an error
    json_obj.push(data);
    writeFileSync(path, JSON.stringify(json_obj, null, 4));
}
const addToStatusFile = async (data, fileName) => {
    //TODO: if file does not exist create an empty file with []
    let fileContents = await readFile(fileName, { encoding: 'utf8' });
    let fileObjects = JSON.parse(fileContents);
    fileObjects.push(data);
    await writeFile(fileName, JSON.stringify(fileContents, null, 2), { encoding: 'utf8' });
};
const testLoad = async (fileName) => {
    let fileContents = await readFile(fileName, { encoding: 'utf8' });
    let fileObjects = [JSON.parse(fileContents)];
    if (fileObjects.length > 0) {
        console.log(fileObjects[0].id);
        fileObjects.push(fileObjects[0]);
        await writeFile(fileName, JSON.stringify(fileObjects, null, 2), { encoding: 'utf8' });
    }
    else {
        console.log("not an array");
        let newArray = [];
        newArray.push(fileObjects);
        console.log(newArray);
    }
    // fileObjects.push(data);
    // await writeFile(fileName, JSON.stringify(fileContents, null, 2), { encoding: 'utf8' });
};
const addToStatusFile2 = async (data, fileName) => {
    let fileContents = await readFile(fileName, { encoding: 'utf8' });
    let fileObjects = JSON.parse(fileContents);
    let arrayToUse = [];
    if (fileObjects.length > 0) {
        console.log(fileObjects[0].id);
        arrayToUse = fileObjects;
    }
    else {
        console.log("not an array");
        arrayToUse.push(...fileObjects);
    }
    // fileObjects.push(data);
    // await writeFile(fileName, JSON.stringify(fileContents, null, 2), { encoding: 'utf8' });
};
testLoad("musings.json");

json_tests.ts

import { readFile, writeFile } from 'fs/promises';
import { readFileSync, writeFileSync } from 'fs';
function writeToJson(path, data, rewrite = false) {
    let old_data = readFileSync(path);
    if (old_data.length == 0 || rewrite == true) {
        writeFileSync(path, JSON.stringify(data, null, 4));
        return;
    }
    let json_obj = [JSON.parse(old_data)]; // without brackets it reverts an error
    json_obj.push(data);
    writeFileSync(path, JSON.stringify(json_obj, null, 4));
}
const addToStatusFile = async (data, fileName) => {
    //TODO: if file does not exist create an empty file with []
    let fileContents = await readFile(fileName, { encoding: 'utf8' });
    let fileObjects = JSON.parse(fileContents);
    fileObjects.push(data);
    await writeFile(fileName, JSON.stringify(fileContents, null, 2), { encoding: 'utf8' });
};
const testLoad = async (fileName) => {
    let fileContents = await readFile(fileName, { encoding: 'utf8' });
    let fileObjects = [JSON.parse(fileContents)];
    if (fileObjects.length > 0) {
        console.log(fileObjects[0].id);
        fileObjects.push(fileObjects[0]);
        await writeFile(fileName, JSON.stringify(fileObjects, null, 2), { encoding: 'utf8' });
    }
    else {
        console.log("not an array");
        let newArray = [];
        newArray.push(fileObjects);
        console.log(newArray);
    }
    // fileObjects.push(data);
    // await writeFile(fileName, JSON.stringify(fileContents, null, 2), { encoding: 'utf8' });
};
const addToStatusFile2 = async (data, fileName) => {
    let fileContents = await readFile(fileName, { encoding: 'utf8' });
    let fileObjects = JSON.parse(fileContents);
    let arrayToUse = [];
    if (fileObjects.length > 0) {
        console.log(fileObjects[0].id);
        arrayToUse = fileObjects;
    }
    else {
        console.log("not an array");
        arrayToUse.push(...fileObjects);
    }
    // fileObjects.push(data);
    // await writeFile(fileName, JSON.stringify(fileContents, null, 2), { encoding: 'utf8' });
};
testLoad("musings.json");

musings.json

{
      "id": "109803445656514120",
      "createdAt": "2023-02-03T23:40:15.608Z",
      "inReplyToId": null,
      "inReplyToAccountId": null,
      "sensitive": false,
      "spoilerText": "",
      "visibility": "public",
      "language": "en",
      "uri": "https://social.cozytronics.com/users/tipsyrobot/statuses/109803445656514120",
      "url": "https://social.cozytronics.com/@tipsyrobot/109803445656514120",
      "repliesCount": 0,
      "reblogsCount": 0,
      "favouritesCount": 0,
      "editedAt": null,
      "favourited": false,
      "reblogged": false,
      "muted": false,
      "bookmarked": false,
      "pinned": false,
      "content": "<p>But I&#39;m just rambling, not caring if any of it actually gets through...</p>",
      "filtered": [],
      "reblog": null,
      "application": {
        "name": "Tipsy Robot",
        "website": null
      },
      "account": {
        "id": "109802669824115839",
        "username": "tipsyrobot",
        "acct": "tipsyrobot",
        "displayName": "tipsyrobot",
        "locked": false,
        "bot": true,
        "discoverable": false,
        "group": false,
        "createdAt": "2023-02-03T00:00:00.000Z",
        "note": "",
        "url": "https://social.cozytronics.com/@tipsyrobot",
        "avatar": "https://social.cozytronics.com/avatars/original/missing.png",
        "avatarStatic": "https://social.cozytronics.com/avatars/original/missing.png",
        "header": "https://social.cozytronics.com/headers/original/missing.png",
        "headerStatic": "https://social.cozytronics.com/headers/original/missing.png",
        "followersCount": 0,
        "followingCount": 1,
        "statusesCount": 11,
        "lastStatusAt": "2023-02-03",
        "noindex": false,
        "emojis": [],
        "fields": []
      },
      "mediaAttachments": [],
      "mentions": [],
      "tags": [],
      "emojis": [],
      "card": null,
      "poll": null
}

Here's how I might do it:

import { readFile, writeFile } from 'fs/promises';

const appendObjectToFile = async(myobj,filename) => {
    let objs = [];  // in case there are none
    // attempt to read and parse file, if fail, we have new objs array above
    try {
        let contents = await readFile(filename, { encoding: 'utf8' });
        objs = JSON.parse(contents)
    } catch (e) {
        console.log("appendObjectToFile error:",e.message);
        console.log("starting new file");
    }
    // add to object array
    objs.push(myobj)
    // save combined obj array to file
    await writeFile(filename, JSON.stringify(objs, null, 2), { encoding: 'utf8' });
};

console.log("writing first object")
let myobj1 = { name:'Maxipants', alignment:"mostly evil"}
await appendObjectToFile(myobj1, "catlog.json")

console.log("writing second object")
let myobj2 = { name:'Crookshanks', alignment:"chaotic hunger"}
await appendObjectToFile(myobj2, "catlog.json")

console.log("writing third object")
let myobj3 = { name:'Claret', alignment:"sproingy neutral"}
await appendObjectToFile(myobj3, "catlog.json")