doesitarm/helpers/lite-youtube.js
2021-05-15 13:11:07 -05:00

107 lines
4.3 KiB
JavaScript

// 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)