Download FB messenger chat / group chat to txt file (for PL language)

download.js

/* Releases
- 1.0.0 Initial
- 1.0.1 Remove '\n' between each msg
*/

const config = {
	numbered: true,                                   // whether to number the messages
	yourResponsesMargin: 90,                          // amount of ' ' char
	msgsSelector: '__fb-dark-mode x1n2onr6',          // message block class (10.11.2023 for first open from right)
	defaultChatEmoji: [ 'Gest kciuka w górę', '👍' ], // [string for default emoji ; what to replaec it with]
};

let msgStrsArr = [];
let msgsTranscript = '';
const msgs = [...document.getElementsByClassName(config.msgsSelector)]; // <- getting all available msgs (from popoup on the bottom right side - needs to be scrolled far enough to get all msgs)

const download = (filename, text) => { // dynamically creates and automatically downloads text file with given content
  const el = document.createElement('a');
  el.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
  el.setAttribute('download', filename);

  el.style.display = 'none';
  document.body.appendChild(el);

  el.click();

  document.body.removeChild(el);
};

msgs.map(el => {
	const personName = el.getElementsByTagName('span')[0]?.textContent;
	let msg = el.textContent;

	// separating between duplicate msgs (picking one with 'trash' strings)
	if (msg.includes('Otwórz')) {
		// removing 'trash' strs
		msg = msg.replace('Wysłano', '').replace('Otwórz', '');

		// replacing default chat emoji
		msg = msg.replace(...config.defaultChatEmoji);

		// removing person's name and adding margin to your msgs
		msg = '\n' + (msg.includes(personName) ? msg.replace(personName, '') : ' '.repeat(config.yourResponsesMargin) + msg)
		//            ^ checking who sent the msg   ^ removing friend's name      ^ adding margin to your msgs
		
		// temp img solution
		if (msg === '\n') msg = '\n~img~';

		if (config.numbered) {
			msgStrsArr.push(msg);
		} else {
			msgsTranscript += msg;
		};
	};
});

// adding nums to msgs
if (config.numbered) {
	const maxCountStrLen = msgStrsArr.length.toString().length;
	//msgStrsArr = msgStrsArr.reverse();
	for (let i = 0; i < msgStrsArr.length; i++) {
		msgsTranscript += '\n{' + (i + 1).toString().padStart(maxCountStrLen, '0') + '} ' + msgStrsArr[i].substring(1);
		//                                                                              removes first `\n` ^
	};
};

// Start download of output file
download('transcript.txt', msgsTranscript.substring(2));
//             removes the first 2x `\n` ^

scroll.js

// goofy solution a lot to fix but hey, it works

// Config:
let counter = 0;
let iterations = 200;
let delay = 500;

let scrollCount = 0;

for (let i = 0; i < iterations; i++) {
  console.log(`${counter += 1} / ${iterations}`);

  const msgContainer = document.querySelector("#mount_0_0_5b > div > div:nth-child(1) > div > div:nth-child(6) > div > div.xuk3077.x78zum5.xc8icb0 > div.x1ey2m1c.x78zum5.x164qtfw.xixxii4.x1vjfegm > div > div > div > div > div > div.x78zum5.xdt5ytf.x1iyjqo2.x193iq5w.x2lwn1j.x1n2onr6 > div.x78zum5.xdt5ytf.x1iyjqo2 > div > div > div > div > div > div")
  
  // scroll up till the next batch loads
  msgContainer.scroll(0, scrollCount -= 9999999);
  
  // some delay before next scroll
  await new Promise(resolve => setTimeout(resolve, delay));
};