Fetch entire Discord conversation to json

const Discord = require('discord.js');
const client = new Discord.Client();
const hideriToken = "TOKEN";
const hideriId = "BOT USER ID"; // unused
const fetchLimit = 50;
const cdTime = 3000;

var allTexts = [];
var bckFile = 0;

const fs = require('fs');

/**
 * @returns Promise<string> contents
 */
function fileWrite(path, content, options) {
    return new Promise((resolve, reject) => {
        var callback = (err, data) => {
            if (err) reject(err);
            else resolve(data);
        };
        fs.writeFile(path, content, options ? options : callback, options ? callback : null);
    });
}

function sleep(time) {
    return new Promise(resolve => setTimeout(resolve, time));
}

client.on('ready', () => {
    console.log(`Logged in as ${client.user.tag}!`);
    let alexaChan = client.channels.get("ID"); // id of DM channel to back up

    async function processMessages(msgs) {
        let last = undefined;
        for (let entry of msgs.entries()) {
            let msg = entry[1];
            let id = entry[0];
            last = id;
            let msgObj = {
                id: id,
                content: msg.content,
                created: msg.createdAt,
                author: msg.author.tag
            };
            if (msg.attachments.size > 0) {
                let attachs = [];
                for (let attachEntry of msg.attachments.entries()) {
                    let attach = attachEntry[1];
                    attachs.push(attach.url);
                }
                msgObj.attachments = attachs;
            }
            allTexts.push(msgObj);
        }
        return last;
    }

    async function fetchNext(before) {
        let options = { limit: fetchLimit };
        if (before) {
            options.before = before;
        }
        alexaChan.fetchMessages(options).then(async (msgs) => {
            newBefore = await processMessages(msgs);
            console.log('targetFolder/backup' + bckFile + ".json");
            await fileWrite('targetFolder/backup' + bckFile + ".json", JSON.stringify(allTexts), 'utf8');
            bckFile++;
            if (msgs.size >= fetchLimit) {
                await sleep(cdTime);
                fetchNext(newBefore);
            }
        });
    }

    fetchNext();
});

client.login(hideriToken);