https://gorouichi-chuomachiten.com/wp-content/themes/theme001_re/js/lite-yt-embed.js?ver=7.1.2

1/**
2 * A lightweight youtube embed. Still should feel the same to the user, just MUCH faster to initialize and paint.
3 *
4 * Thx to these as the inspiration
5 *   https://storage.googleapis.com/amp-vs-non-amp/youtube-lazy.html
6 *   https://autoplay-youtube-player.glitch.me/
7 *
8 * Once built it, I also found these:
9 *   https://github.com/ampproject/amphtml/blob/master/extensions/amp-youtube (👍👍)
10 *   https://github.com/Daugilas/lazyYT
11 *   https://github.com/vb/lazyframe
12 */
13class LiteYTEmbed extends HTMLElement {
14    connectedCallback() {
15        this.videoId = this.getAttribute('videoid');
16
17        let playBtnEl = this.querySelector('.lty-playbtn');
18        // A label for the button takes priority over a [playlabel] attribute on the custom-element
19        this.playLabel = (playBtnEl && playBtnEl.textContent.trim()) || this.getAttribute('playlabel') || 'Play';
20
21        /**
22         * Lo, the youtube placeholder image!  (aka the thumbnail, poster image, etc)
23         *
24         * See https://github.com/paulirish/lite-youtube-embed/blob/master/youtube-thumbnail-urls.md
25         *
26         * TODO: Do the sddefault->hqdefault fallback
27         *       - When doing this, apply referrerpolicy (https://github.com/ampproject/amphtml/pull/3940)
28         * TODO: Consider using webp if supported, falling back to jpg
29         */
30        if (!this.style.backgroundImage) {
31          this.style.backgroundImage = `url("https://i.ytimg.com/vi/${this.videoId}/hqdefault.jpg")`;
32        }
33
34        // Set up play button, and its visually hidden label
35        if (!playBtnEl) {
36            playBtnEl = document.createElement('button');
37            playBtnEl.type = 'button';
38            playBtnEl.classList.add('lty-playbtn');
39            this.append(playBtnEl);
40        }
41        if (!playBtnEl.textContent) {
42            const playBtnLabelEl = document.createElement('span');
43            playBtnLabelEl.className = 'lyt-visually-hidden';
44            playBtnLabelEl.textContent = this.playLabel;
45            playBtnEl.append(playBtnLabelEl);
46        }
47        playBtnEl.removeAttribute('href');
48
49        // On hover (or tap), warm up the TCP connections we're (likely) about to use.
50        this.addEventListener('pointerover', LiteYTEmbed.warmConnections, {once: true});
51
52        // Once the user clicks, add the real iframe and drop our play button
53        // TODO: In the future we could be like amp-youtube and silently swap in the iframe during idle time
54        //   We'd want to only do this for in-viewport or near-viewport ones: https://github.com/ampproject/amphtml/pull/5003
55        this.addEventListener('click', this.addIframe);
56
57        // Chrome & Edge desktop have no problem with the basic YouTube Embed with ?autoplay=1
58        // However Safari desktop and most/all mobile browsers do not successfully track the user gesture of clicking through the creation/loading of the iframe,
59        // so they don't autoplay automatically. Instead we must load an additional 2 sequential JS files (1KB + 165KB) (un-br) for the YT Player API
60        // TODO: Try loading the the YT API in parallel with our iframe and then attaching/playing it. #82
61        this.needsYTApiForAutoplay = navigator.vendor.includes('Apple') || navigator.userAgent.includes('Mobi');
62    }
63
64    /**
65     * Add a <link rel={preload | preconnect} ...> to the head
66     */
67    static addPrefetch(kind, url, as) {
68        const linkEl = document.createElement('link');
69        linkEl.rel = kind;
70        linkEl.href = url;
71        if (as) {
72            linkEl.as = as;
73        }
74        document.head.append(linkEl);
75    }
76
77    /**
78     * Begin pre-connecting to warm up the iframe load
79     * Since the embed's network requests load within its iframe,
80     *   preload/prefetch'ing them outside the iframe will only cause double-downloads.
81     * So, the best we can do is warm up a few connections to origins that are in the critical path.
82     *
83     * Maybe `<link rel=preload as=document>` would work, but it's unsupported: http://crbug.com/593267
84     * But TBH, I don't think it'll happen soon with Site Isolation and split caches adding serious complexity.
85     */
86    static warmConnections() {
87        if (LiteYTEmbed.preconnected) return;
88
89        // The iframe document and most of its subresources come right off youtube.com
90        LiteYTEmbed.addPrefetch('preconnect', 'https://www.youtube-nocookie.com');
91        // The botguard script is fetched off from google.com
92        LiteYTEmbed.addPrefetch('preconnect', 'https://www.google.com');
93
94        // Not certain if these ad related domains are in the critical path. Could verify with domain-specific throttling.
95        LiteYTEmbed.addPrefetch('preconnect', 'https://googleads.g.doubleclick.net');
96        LiteYTEmbed.addPrefetch('preconnect', 'https://static.doubleclick.net');
97
98        LiteYTEmbed.preconnected = true;
99    }
100
101    fetchYTPlayerApi() {
102        if (window.YT || (window.YT && window.YT.Player)) return;
103
104        this.ytApiPromise = new Promise((res, rej) => {
105            var el = document.createElement('script');
106            el.src = 'https://www.youtube.com/iframe_api';
107            el.async = true;
108            el.onload = _ => {
109                YT.ready(res);
110            };
111            el.onerror = rej;
112            this.append(el);
113        });
114    }
115
116    async addYTPlayerIframe(params) {
117        this.fetchYTPlayerApi();
118        await this.ytApiPromise;
119
120        const videoPlaceholderEl = document.createElement('div')
121        this.append(videoPlaceholderEl);
122

123        const paramsObj = Object.fromEntries(params.entries());
124
125        new YT.Player(videoPlaceholderEl, {
126            width: '100%',
127            videoId: this.videoId,
128            playerVars: paramsObj,
129            events: {
130                'onReady': event => {
131                    event.target.playVideo();
132                }
133            }
134        });
135    }
136
137    async addIframe(){
138        if (this.classList.contains('lyt-activated')) return;
139        this.classList.add('lyt-activated');
140
141        const params = new URLSearchParams(this.getAttribute('params') || []);
142        params.append('autoplay', '1');
143        params.append('playsinline', '1');
144
145        if (this.needsYTApiForAutoplay) {
146            return this.addYTPlayerIframe(params);
147        }
148
149        const iframeEl = document.createElement('iframe');
150        iframeEl.width = 560;
151        iframeEl.height = 315;
152        // No encoding necessary as [title] is safe. https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html#:~:text=Safe%20HTML%20Attributes%20include
153        iframeEl.title = this.playLabel;
154        iframeEl.allow = 'accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture';
155        iframeEl.allowFullscreen = true;
156        // AFAIK, the encoding here isn't necessary for XSS, but we'll do it only because this is a URL
157        // https://stackoverflow.com/q/64959723/89484
158        iframeEl.src = `https://www.youtube-nocookie.com/embed/${encodeURIComponent(this.videoId)}?${params.toString()}`;
159        this.append(iframeEl);
160
161        // Set focus for a11y
162        iframeEl.focus();
163    }
164}
165// Register custom element
166customElements.define('lite-youtube', LiteYTEmbed);