Add basic player component

helpers/lite-youtube.js

@@ -0,0 +1,107 @@
+// https://github.com/paulirish/lite-youtube-embed/blob/master/src/lite-yt-embed.js
+
+// import canAutoPlay from 'can-autoplay'
+
+
+/**
+ * A lightweight youtube embed. Still should feel the same to the user, just MUCH faster to initialize and paint.
+ *
+ * Thx to these as the inspiration
+ *   https://storage.googleapis.com/amp-vs-non-amp/youtube-lazy.html
+ *   https://autoplay-youtube-player.glitch.me/
+ *
+ * Once built it, I also found these:
+ *   https://github.com/ampproject/amphtml/blob/master/extensions/amp-youtube (👍👍)
+ *   https://github.com/Daugilas/lazyYT
+ *   https://github.com/vb/lazyframe
+ */
+class LiteYTEmbed extends HTMLElement {
+    constructor() {
+        // Always call super first in constructor
+        super()
+
+        // write element functionality in here
+
+        // console.log('canAutoplay', canAutoplay)
+
+    }
+
+    connectedCallback() {
+        this.videoId = this.getAttribute('videoid')
+
+        console.log('canAutoplay from connectedCallback', canAutoplay)
+
+        // On hover (or tap), warm up the TCP connections we're (likely) about to use.
+        this.addEventListener('pointerover', LiteYTEmbed.warmConnections, {once: true})
+
+        // Once the user clicks, add the real iframe and drop our play button
+        // TODO: In the future we could be like amp-youtube and silently swap in the iframe during idle time
+        //   We'd want to only do this for in-viewport or near-viewport ones: https://github.com/ampproject/amphtml/pull/5003
+        this.addEventListener('click', e => this.addIframe())
+    }
+
+    // // TODO: Support the the user changing the [videoid] attribute
+    // attributeChangedCallback() {
+    // }
+
+    /**
+     * Add a <link rel={preload | preconnect} ...> to the head
+     */
+    static addPrefetch(kind, url, as) {
+        const linkEl = document.createElement('link')
+        linkEl.rel = kind
+        linkEl.href = url
+        if (as) {
+            linkEl.as = as
+        }
+        document.head.append(linkEl)
+    }
+
+    /**
+     * Begin pre-connecting to warm up the iframe load
+     * Since the embed's network requests load within its iframe,
+     *   preload/prefetch'ing them outside the iframe will only cause double-downloads.
+     * So, the best we can do is warm up a few connections to origins that are in the critical path.
+     *
+     * Maybe `<link rel=preload as=document>` would work, but it's unsupported: http://crbug.com/593267
+     * But TBH, I don't think it'll happen soon with Site Isolation and split caches adding serious complexity.
+     */
+    static warmConnections() {
+        if (LiteYTEmbed.preconnected) return
+
+        // The iframe document and most of its subresources come right off youtube.com
+        LiteYTEmbed.addPrefetch('preconnect', 'https://www.youtube-nocookie.com')
+        // The botguard script is fetched off from google.com
+        LiteYTEmbed.addPrefetch('preconnect', 'https://www.google.com')
+
+        // Not certain if these ad related domains are in the critical path. Could verify with domain-specific throttling.
+        LiteYTEmbed.addPrefetch('preconnect', 'https://googleads.g.doubleclick.net')
+        LiteYTEmbed.addPrefetch('preconnect', 'https://static.doubleclick.net')
+
+        LiteYTEmbed.preconnected = true
+    }
+
+    addIframe() {
+        const params = new URLSearchParams(this.getAttribute('params') || [])
+        params.append('autoplay', '1')
+
+        const iframeEl = document.createElement('iframe')
+        iframeEl.width = 560
+        iframeEl.height = 315
+        // No encoding necessary as [title] is safe. https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html#:~:text=Safe%20HTML%20Attributes%20include
+        iframeEl.title = this.playLabel
+        iframeEl.allow = 'accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture'
+        iframeEl.allowFullscreen = true
+        // AFAIK, the encoding here isn't necessary for XSS, but we'll do it only because this is a URL
+        // https://stackoverflow.com/q/64959723/89484
+        iframeEl.src = `https://www.youtube-nocookie.com/embed/${encodeURIComponent(this.videoId)}?${params.toString()}`
+        this.append(iframeEl)
+
+        this.classList.add('lyt-activated')
+
+        // Set focus for a11y
+        this.querySelector('iframe').focus()
+    }
+}
+// Register custom element
+window.customElements.define('lite-youtube', LiteYTEmbed)