Skip to content

Instantly share code, notes, and snippets.

@pmeenan
Created November 8, 2021 20:21
Show Gist options
  • Save pmeenan/40a0a63d505ee8aec429dfe73f8a0723 to your computer and use it in GitHub Desktop.
Save pmeenan/40a0a63d505ee8aec429dfe73f8a0723 to your computer and use it in GitHub Desktop.
Adding Priority Hints with Cloudflare Workers
addEventListener('fetch', event => {
event.respondWith(handleRequest(event.request))
});
async function handleRequest(request) {
const url = new URL(request.url);
const host = request.headers.get('x-host');
if(!host) {
return new Response('x-host header missing', {status: 403});
}
url.hostname = host;
const bypassTransform = request.headers.get('x-bypass-transform');
const acceptHeader = request.headers.get('accept');
if((acceptHeader && acceptHeader.indexOf('text/html') >= 0) &&
(!bypassTransform || (bypassTransform && bypassTransform.indexOf('true') === -1))) {
const response = await fetch(url.toString(), request);
return new HTMLRewriter()
.on('div.has-hero>div.content>article.story-1>div.m>a>picture>img', new prioritizeHigh() /* Fox News */)
.on('img.pica-circus', new prioritizeHigh() /* Ling's Cars */)
.on('img#FMP-target', new prioritizeHigh() /* Airbnb */ )
.on('img.mainImageMobile[alt="1"]', new prioritizeHigh() /* Amazon PDP */ )
.on('img[data-carousel-first-image]', new prioritizeHigh() /* etsy */ )
.on('img.primary-image', new prioritizeHigh() /* BestBuy */ )
.on('img[elementtiming="TTVR.Infopane"]', new prioritizeHigh() /* MSN */)
.on('img[src$="learn_hero.jpg"]', new prioritizeHigh() /* developers.google.com */)
.on('img.rYD0Re', new prioritizeHigh() /* Google Flights */)
.on('img.dn', new prioritizeHigh() /* Cloudflare blog */)
.transform(response);
}
// Otherwise just proxy the request
return fetch(url.toString(), request)
}
class prioritizeHigh {
element(element) {
element.removeAttribute('loading');
element.setAttribute('importance', 'high');
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment