Zoom Recording Playback Auto-Scroll Chat

zoom-scroll.js

// Set this to the number of seconds off that the chat is from the video
var chatOffset = 0;

const vid = $('video');
const chat = $('.zm-scrollbar__view ul');
const messages = chat.querySelectorAll('li .chat-time');
let lastTime = undefined;

function pad(num) {
	return String(num).padStart(2, '0');
}

function parseTime(str) {
	const nums = /(\d\d)?:?(\d\d):(\d\d)/.exec(str);
	let time = 0;
	if (nums[1]) {
		time = parseInt(nums[1]) * 60 * 60;
	}
	time += parseInt(nums[2]) * 60 + parseInt(nums[3]);
	return time;
}

function viewChat(msg) {
	msg.parentElement.parentElement.scrollIntoView({
		behavior: 'smooth',
		block: 'end'
	});
}

vid.addEventListener('timeupdate', (e) => {
	const time = Math.floor(vid.currentTime + chatOffset);
	if (lastTime !== time) {
		lastTime = time;

		const sec = pad(time % 60);
		const min = pad(Math.floor(time / 60) % 60);
		const hour = pad(Math.floor(time / 60 / 60));

		let low = 0, high = messages.length - 1;
		while (low <= high) {
			let i = Math.floor(low + (high - low) / 2);
			const msg = messages[i];
			const timeStr = `${hour !== '00' ? hour + ':' : ''}${min}:${sec}`;
			if (msg.textContent === timeStr) {
				viewChat(msg);
				return;
			} else {
				const mtime = parseTime(msg.textContent);
				if (time > mtime) {
					low = i + 1;
				} else {
					high = i - 1;
				}
			}
		}
		if (high >= 0)
			viewChat(messages[high]);
	}
});

zoom-scroll.min.js

var chatOffset=0;const vid=$("video"),chat=$(".zm-scrollbar__view ul"),messages=chat.querySelectorAll("li .chat-time");let lastTime=void 0;function pad(t){return String(t).padStart(2,"0")}function parseTime(t){const e=/(\d\d)?:?(\d\d):(\d\d)/.exec(t);let a=0;return e[1]&&(a=60*parseInt(e[1])*60),a+=60*parseInt(e[2])+parseInt(e[3])}function viewChat(t){t.parentElement.parentElement.scrollIntoView({behavior:"smooth",block:"end"})}vid.addEventListener("timeupdate",t=>{const e=Math.floor(vid.currentTime+chatOffset);if(lastTime!==e){lastTime=e;const t=pad(e%60),a=pad(Math.floor(e/60)%60),n=pad(Math.floor(e/60/60));let s=0,o=messages.length-1;for(;s<=o;){let r=Math.floor(s+(o-s)/2);const i=messages[r],l=`${"00"!==n?n+":":""}${a}:${t}`;if(i.textContent===l)return void viewChat(i);e>parseTime(i.textContent)?s=r+1:o=r-1}o>=0&&viewChat(messages[o])}});

How to Use

Open your dev tools (F12 is most browsers), go to the console tab, and paste in the above snippet (.min.js is recommended). Press enter once you see that the Zoom Chat window on the right has appeared.

Updates

Update 6/7/2020 @ 11:09PM EST:
Uses binary search to select chat item. Fixed chat not scrolling after past 1 hour mark. Chat scrolls to the previous message at a timestamp where there is no message.

Update 8/30/2020:
Sometimes the chat and video timestamps won't line up, so you can set chatOffset in either the source code or in the console to the number of seconds off that chat is from the video.