The following works fine in a browser (by creating a service worker)
addEventListener('fetch', event => {
event.respondWith(fetchAndApply(event.request))
})
async function fetchAndApply(request) {
try {
const LanguageRes = await fetch('https://cdn.jsdelivr.net/gh/collinbarrett/FilterLists/data/Language.json')
const Language = await LanguageRes.text()
return new Response(JSON.stringify(JSON.parse(Language)))
// This throws an internal error
//const Language = await LanguageRes.json()
//return new Response(JSON.stringify(Language))
} catch (err) {
return new Response(err.stack || err)
}
}
content-length: 126
content-type: text/plain;charset=UTF-8
SyntaxError: Unexpected token  in JSON at position 0
at JSON.parse (<anonymous>)
at fetchAndApply (worker.js:10:45)