YouTube Jump Ahead Shortcut User Script

script.js

// ==UserScript==
// @name         YouTube Jump Ahead Shortcut
// @namespace    https://aht.cx/userscripts/youtube-jump-ahead-shortcut
// @version      1.0
// @description  Keyboard shortcut for the "Jump ahead" button available to YouTube Premium users
// @match        https://www.youtube.com/watch*
// @run-at       document-end
// @grant        none
// ==/UserScript==

(function () {
	"use strict";

	const TRIGGER_KEYS = ["s", "S"];
	const TARGET_BUTTON_TEXT = "Jump ahead";
	const WAIT_TIMEOUT_MS = 2000;
	const POLL_INTERVAL_MS = 50;

	const ARROW_RIGHT_EVENT = {
		key: "ArrowRight",
		code: "ArrowRight",
		keyCode: 39,
		which: 39,
		bubbles: true,
		cancelable: true,
	};

	const getPlayer = () => document.querySelector(".html5-video-player");

	const isTypingTarget = (el) => !!el && (el.tagName === "INPUT" || el.tagName === "TEXTAREA" || el.isContentEditable);

	const normalizeText = (s) => (s || "").trim().replace(/\s+/g, " ").toLowerCase();

	const isClickableVisible = (el) => {
		if (!el) return false;
		if (el.getAttribute("aria-disabled") === "true" || el.disabled) return false;
		const rect = el.getBoundingClientRect();
		return rect.width > 0 && rect.height > 0;
	};

	const dispatchRightArrow = (target) => {
		target.dispatchEvent(new KeyboardEvent("keydown", ARROW_RIGHT_EVENT));
		target.dispatchEvent(new KeyboardEvent("keyup", ARROW_RIGHT_EVENT));
	};

	const findButtonByText = (player, label) => {
		const needle = normalizeText(label);

		for (const el of player.querySelectorAll('button, [role="button"]')) {
			if (normalizeText(el.textContent) !== needle) continue;
			if (isClickableVisible(el)) return el;
		}

		for (const el of player.querySelectorAll('button, [role="button"]')) {
			if (!normalizeText(el.textContent).includes(needle)) continue;
			if (isClickableVisible(el)) return el;
		}

		return null;
	};

	const waitForButtonAndClick = (player, label, timeoutMs, pollMs) =>
		new Promise((resolve) => {
			const startedAt = Date.now();
			let pollTimer = null;
			let observer = null;

			const cleanup = (result) => {
				if (pollTimer) clearInterval(pollTimer);
				if (observer) observer.disconnect();
				resolve(result);
			};

			const attempt = () => {
				const btn = findButtonByText(player, label);
				if (btn) {
					setTimeout(() => btn.click(), 0);
					return cleanup(true);
				}
				if (Date.now() - startedAt >= timeoutMs) cleanup(false);
			};

			observer = new MutationObserver(() => requestAnimationFrame(attempt));
			observer.observe(player, {
				childList: true,
				subtree: true,
				characterData: true,
				attributes: true,
			});

			pollTimer = setInterval(attempt, pollMs);
			attempt();
		});

	const doAction = async () => {
		const player = getPlayer();
		if (!player) return;

		dispatchRightArrow(document);
		dispatchRightArrow(player);

		await waitForButtonAndClick(player, TARGET_BUTTON_TEXT, WAIT_TIMEOUT_MS, POLL_INTERVAL_MS);
	};

	document.addEventListener(
		"keydown",
		(event) => {
			if (isTypingTarget(event.target)) return;
			if (!TRIGGER_KEYS.includes(event.key)) return;

			event.preventDefault();
			event.stopPropagation();
			void doAction();
		},
		true,
	);
})();