Set Player Volume

Set youtube player volume using userscript menu command using prompt()
换行
// ==UserScript==
// @name         Set Player Volume
// @namespace    https://greasyfork.org/users/1201646
// @version      1.0
// @description  Set youtube player volume using userscript menu command using prompt()
// @author       nemonai~
// @match        https://www.youtube.com/watch*
// @icon         https://icons.duckduckgo.com/ip2/youtube.com.ico
// @grant        GM_registerMenuCommand
// @run-at       document-idle
// @license      MIT
// ==/UserScript==


(() => {
	'use strict';
	GM_registerMenuCommand('Volume', () => {
		let num = prompt('Enter new volume', document.getElementById('movie_player').getVolume());

		if (num !== null) {
			num = Number(num);

			if (!Number.isNaN(num) && num !== document.getElementById('movie_player').getVolume()) {
				if (num > 100) { num = 100; }
				if (num <   0) { num =   0; }
				document.getElementById('movie_player').setVolume(num);
			}
		}
	});
})();