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Undo and redo changes in playback position on YouTube
// ==UserScript==
// @name YouTube Undo
// @description Undo and redo changes in playback position on YouTube
// @version 0.2.0
// @author Adam Thompson-Sharpe
// @namespace MysteryBlokHed
// @license GPL-3.0
// @copyright 2022 Adam Thomspon-Sharpe
// @homepageURL https://gitlab.com/MysteryBlokHed/userscripts/-/tree/main/YouTubeUndo
// @supportURL https://gitlab.com/MysteryBlokHed/userscripts/-/issues
// @match *://*.youtube.com/watch*
// @grant none
// ==/UserScript==
;(() => {
var _a
/** Whether to log basic debug events */
const DEBUG_LOGS = false
const debug = DEBUG_LOGS
? (...args) => console.debug('[YouTube Undo]', ...args)
: () => {}
/** The interval **in seconds** to check the player's current time */
const ROUGH_TIME_RATE = 2
/** Keep track of the current player time while no events are in the array */
let roughTime = 0
setInterval(() => {
const currentTime = player.getCurrentTime()
roughTime = currentTime
}, ROUGH_TIME_RATE * 1000)
/**
* Track the index in the array that matches the current state of undo's/redo's.
* Used to allow undoing and redoing back and forth
*/
let undoPoint = -1
/** Time change events */
const timeChanges = []
const addChange = change => {
debug('Adding change event to', timeChanges)
timeChanges.length = undoPoint + 1
timeChanges.push(change)
undoPoint = timeChanges.length - 1
debug('After:', timeChanges)
}
/** The current time change event, using `undoPoint` */
const currentChange = () => {
var _a
return (_a = timeChanges[undoPoint]) !== null && _a !== void 0 ? _a : null
}
/** The last time change event in the list */
const lastChange = () =>
timeChanges.length ? timeChanges[timeChanges.length - 1] : null
/** Get the last change's time if it exists, otherwise use the rough time */
const lastOrRough = () => {
var _a, _b
return (_b =
(_a = lastChange()) === null || _a === void 0 ? void 0 : _a.after) !==
null && _b !== void 0
? _b
: roughTime
}
// prettier-ignore
const player = document.getElementById('movie_player');
if (!player) {
console.error('[YouTube Undo]', 'Player not found!')
return
}
// Clear events on location changes
window.addEventListener('yt-navigate-finish', () => {
timeChanges.length = 0
undoPoint = -1
debug('New video, clearing event list')
})
// Watch for playbar clicks
;(_a = document.querySelector('div.ytp-progress-bar')) === null ||
_a === void 0
? void 0
: _a.addEventListener('click', () => {
const currentTime = player.getCurrentTime()
addChange({
before: lastOrRough(),
after: currentTime,
})
roughTime = currentTime
debug('Added time change for playbar seek', lastChange())
})
// Watch for keypresses
window.addEventListener('keydown', ev => {
if (ev.key.match(/^(?:\d|j|l|ArrowLeft|ArrowRight)$/i)) {
// A key that might change the current time
const last = lastChange()
const currentTime = player.getCurrentTime()
debug('Time-changing key pressed')
debug('Last:', last)
debug('Current:', currentTime)
if (!last) debug('Rough Time:', roughTime)
if (
(last === null || last === void 0 ? void 0 : last.after) !== currentTime
) {
addChange({
before: lastOrRough(),
after: currentTime,
})
}
} else if (ev.ctrlKey && ev.key.toLowerCase() === 'z') {
// Ctrl + Z
const undoTo = currentChange()
debug('Ctrl + Z pressed')
debug('Full list:', timeChanges)
debug('Undoing to:', undoTo, 'at index', undoPoint)
if (undoTo) player.seekTo(undoTo.before)
if (undoPoint >= 0) undoPoint--
} else if (ev.ctrlKey && ev.key.toLowerCase() === 'y') {
// Ctrl + Y
if (undoPoint < timeChanges.length - 1) undoPoint++
const redoTo = currentChange()
debug('Ctrl + Y pressed')
debug('Full list:', timeChanges)
debug('Redoing to:', redoTo, 'at index', undoPoint)
if (redoTo) player.seekTo(redoTo.after)
}
})
})()