https://www.basketnews.lt/assets/javascript/lite-yt-embed.js?v=1.5.0.5

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          const quality = this.getAttribute('posterquality') || 'hqdefault';
32          this.style.backgroundImage = `url("https://i.ytimg.com/vi/${this.videoId}/${quality}.jpg")`;
33        }
34
35        // Set up play button, and its visually hidden label
36        if (!playBtnEl) {
37            playBtnEl = document.createElement('button');
38            playBtnEl.type = 'button';
39            playBtnEl.classList.add('lty-playbtn');
40            this.append(playBtnEl);
41        }
42        if (!playBtnEl.textContent) {
43            const playBtnLabelEl = document.createElement('span');
44            playBtnLabelEl.className = 'lyt-visually-hidden';
45            playBtnLabelEl.textContent = this.playLabel;
46            playBtnEl.append(playBtnLabelEl);
47        }
48        playBtnEl.removeAttribute('href');
49
50        // On hover (or tap), warm up the TCP connections we're (likely) about to use.
51        this.addEventListener('pointerover', LiteYTEmbed.warmConnections, {once: true});
52
53        // Once the user clicks, add the real iframe and drop our play button
54        // TODO: In the future we could be like amp-youtube and silently swap in the iframe during idle time
55        //   We'd want to only do this for in-viewport or near-viewport ones: https://github.com/ampproject/amphtml/pull/5003
56        this.addEventListener('click', this.addIframe);
57
58        // Chrome & Edge desktop have no problem with the basic YouTube Embed with ?autoplay=1
59        // However Safari desktop and most/all mobile browsers do not successfully track the user gesture of clicking through the creation/loading of the iframe,
60        // 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
61        // TODO: Try loading the the YT API in parallel with our iframe and then attaching/playing it. #82
62        this.needsYTApiForAutoplay = navigator.vendor.includes('Apple') || navigator.userAgent.includes('Mobi');
63    }
64
65    /**
66     * Add a <link rel={preload | preconnect} ...> to the head
67     */
68    static addPrefetch(kind, url, as) {
69        const linkEl = document.createElement('link');
70        linkEl.rel = kind;
71        linkEl.href = url;
72        if (as) {
73            linkEl.as = as;
74        }
75        document.head.append(linkEl);
76    }
77
78    /**
79     * Begin pre-connecting to warm up the iframe load
80     * Since the embed's network requests load within its iframe,
81     *   preload/prefetch'ing them outside the iframe will only cause double-downloads.
82     * So, the best we can do is warm up a few connections to origins that are in the critical path.
83     *
84     * Maybe `<link rel=preload as=document>` would work, but it's unsupported: http://crbug.com/593267
85     * But TBH, I don't think it'll happen soon with Site Isolation and split caches adding serious complexity.
86     */
87    static warmConnections() {
88        if (LiteYTEmbed.preconnected) return;
89
90        // The iframe document and most of its subresources come right off youtube.com
91        LiteYTEmbed.addPrefetch('preconnect', 'https://www.youtube.com');
92        // The botguard script is fetched off from google.com
93        LiteYTEmbed.addPrefetch('preconnect', 'https://www.google.com');
94
95        // Not certain if these ad related domains are in the critical path. Could verify with domain-specific throttling.
96        LiteYTEmbed.addPrefetch('preconnect', 'https://googleads.g.doubleclick.net');
97        LiteYTEmbed.addPrefetch('preconnect', 'https://static.doubleclick.net');
98
99        LiteYTEmbed.preconnected = true;
100    }
101
102    fetchYTPlayerApi() {
103        if (window.YT || (window.YT && window.YT.Player)) return;
104
105        this.ytApiPromise = new Promise((res, rej) => {
106            var el = document.createElement('script');
107            el.src = 'https://www.youtube.com/iframe_api';
108            el.async = true;
109            el.onload = _ => {
110                YT.ready(res);
111            };
112            el.onerror = rej;
113            this.append(el);
114        });
115    }
116
117    async addYTPlayerIframe(params) {
118        this.fetchYTPlayerApi();
119        await this.ytApiPromise;
120
121        const videoPlaceholderEl = document.createElement('div')
122        this.append(videoPlaceholderEl);
123

124        const paramsObj = Object.fromEntries(params.entries());
125        const videoId = this.videoId;
126        const firedProgress = {};
127
128        const emitVideoEvent = function (name, detail) {
129            try {
130                if (typeof window.bnTrackGa4 === 'function') {
131                    window.bnTrackGa4(name, detail);
132                }
133                window.dispatchEvent(new CustomEvent('bn-lite-yt-' + (name === 'video_progress' ? 'progress' : 'complete'), { detail: detail }));
134            } catch (e) { /* swallow */ }
135        };
136
137        new YT.Player(videoPlaceholderEl, {
138            width: '100%',
139            videoId: videoId,
140            playerVars: paramsObj,
141            events: {
142                'onReady': event => {
143                    event.target.playVideo();
144                },
145                'onStateChange': event => {
146                    if (!event || !event.data) {
147                        return;
148                    }
149                    if (event.data === YT.PlayerState.ENDED) {
150                        emitVideoEvent('video_complete', {
151                            video_id: videoId,
152                            video_provider: 'youtube',
153                            video_url: 'https://www.youtube.com/watch?v=' + videoId,
154                        });
155                        return;
156                    }
157                    if (event.data !== YT.PlayerState.PLAYING) {
158                        return;
159                    }
160                    const duration = event.target.getDuration ? event.target.getDuration() : 0;
161                    const current = event.target.getCurrentTime ? event.target.getCurrentTime() : 0;
162                    if (!duration) {
163                        return;
164                    }
165                    const percent = Math.floor((current / duration) * 100);
166                    [25, 50, 75].forEach(function (milestone) {
167                        if (percent >= milestone && !firedProgress[milestone]) {
168                            firedProgress[milestone] = true;
169                            emitVideoEvent('video_progress', {
170                                video_id: videoId,
171                                video_provider: 'youtube',
172                                video_url: 'https://www.youtube.com/watch?v=' + videoId,
173                                video_percent: milestone,
174                                video_duration: Math.floor(duration),
175                                autoplay: true,
176                            });
177                        }
178                    });
179                }
180            }
181        });
182    }
183
184    async addIframe(){
185        if (this.classList.contains('lyt-activated')) return;
186        this.classList.add('lyt-activated');
187
188        const params = new URLSearchParams(this.getAttribute('params') || []);
189        params.append('autoplay', '1');
190        params.append('playsinline', '1');
191        if (!params.has('origin')) {
192            params.append('origin', window.location.origin);
193        }
194
195        if (this.needsYTApiForAutoplay) {
196            return this.addYTPlayerIframe(params);
197        }
198
199        const iframeEl = document.createElement('iframe');
200        iframeEl.width = 560;
201        iframeEl.height = 315;
202        // No encoding necessary as [title] is safe. https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html#:~:text=Safe%20HTML%20Attributes%20include
203        iframeEl.title = this.playLabel;
204        iframeEl.allow = 'accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture';
205        iframeEl.allowFullscreen = true;
206        // AFAIK, the encoding here isn't necessary for XSS, but we'll do it only because this is a URL
207        // https://stackoverflow.com/q/64959723/89484
208        iframeEl.src = `https://www.youtube.com/embed/${encodeURIComponent(this.videoId)}?${params.toString()}`;
209        this.append(iframeEl);
210
211        // Set focus for a11y
212        iframeEl.focus();
213    }
214}
215// Register custom element
216customElements.define('lite-youtube', LiteYTEmbed);