Forked from deanhume/client-hints-service-worker.js
Created
November 20, 2015 20:51
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Service Worker & HTTP Client Hints
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"use strict"; | |
self.addEventListener('fetch', function(event) { | |
var request = event.request, | |
url = request.url, | |
url_object = new URL( url ), | |
re_jpg_or_png = /\.(?:jpg|png)$/, | |
supports_webp = false, // pessimism | |
webp_url; | |
// Check if the image is a local jpg or png | |
if ( re_jpg_or_png.test( request.url ) && | |
url_object.origin == location.origin ) { | |
// console.log('WORKER: caught a request for a local PNG or JPG'); | |
// Inspect the accept header for WebP support | |
if ( request.headers.has('accept') ) | |
{ | |
supports_webp = request.headers.get('accept').includes('webp'); | |
} | |
// Browser supports WebP | |
if ( supports_webp ) | |
{ | |
// Make the new URL | |
webp_url = url.substr(0, url.lastIndexOf('.')) + '.webp'; | |
event.respondWith( | |
fetch( | |
webp_url, | |
{ mode: 'no-cors' } | |
) | |
); | |
} | |
} | |
}); |
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