AlttiRi/background.html

## background.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>background.html</title>
    <script src="background.js" type="module"></script>
</head>
<body></body>
</html>

## background.js
const url = "https://giant.gfycat.com/GrimGrossKoodoo.mp4";
chrome.runtime.onConnect.addListener(async function(port) {
    console.log(port);
    if (port.name === "demo-fetch") {
        let i = 0;
        const response = await fetch(url, {cache: "force-cache"});
        const reader = response.body.getReader();
        while (true) {
            const {done, /** @type {Uint8Array} */ value} = await reader.read();
            const blob = new Blob([value]);
            const url = URL.createObjectURL(blob)
            new Promise(resolve => setTimeout(resolve, 1000)).then(() => URL.revokeObjectURL(url));
            port.postMessage({
                done,
                value: url,
                i: i++
            });
            if (done) {
                break;
            }
        }
    }
});

## content.js
let resolve;
let promise;
function updatePromise() {
    promise = new Promise(_resolve => {
        resolve = _resolve;
    });
}
updatePromise();


const port = chrome.runtime.connect({name: "demo-fetch"});
port.onMessage.addListener(async function({done, value, i}) {
    console.log({done, value, i});
    const ab = await fetch(value).then(r => r.arrayBuffer());
    const u8a = new Uint8Array(ab);

    console.log(i, u8a);
    resolve({done, value: u8a, i});
    updatePromise();
});

console.log("Create ReadableStream");
try {
    rs = new ReadableStream({
        async start(controller) {
            while (true) {
                const {done, value} = await promise;
                if (done) {
                    break;
                }
                controller.enqueue(value);
            }
            controller.close();
        }
    });
} catch (e) {
    console.error(e);
}
console.log("ReadableStream is created", rs);

new Response(rs)
    .blob()
    .then(blob => {
        console.log(blob);
        const a = document.createElement("a");
        a.href = URL.createObjectURL(blob);
        a.download = "GrimGrossKoodoo.mp4";
        a.click();
        new Promise(resolve => setTimeout(resolve, 1000)).then(() => URL.revokeObjectURL(a.href));
    });

## manifest.json
{
    "manifest_version": 2,
    "name": "readable-stream-demo",
    "short_name": "rs-demo",
    "description": "ReadableStream demo extension",
    "version": "1.0",
    "content_scripts": [
        {
            "matches": ["<all_urls>"],
            "js": ["content.js"],
            "run_at": "document_start"
        }
    ],
    "background": {
        "page": "background.html",
        "persistent": true
    },
    "permissions": ["<all_urls>", "activeTab", "tabs"]
}

## package.json
{
    "name": "readable-stream-extension-demo",
    "version": "1.0.0",
    "type": "module"
}
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="utf-8">
	<title>background.html</title>
	<script src="background.js" type="module"></script>
	</head>
	<body></body>
	</html>
	const url = "https://giant.gfycat.com/GrimGrossKoodoo.mp4";
	chrome.runtime.onConnect.addListener(async function(port) {
	console.log(port);
	if (port.name === "demo-fetch") {
	let i = 0;
	const response = await fetch(url, {cache: "force-cache"});
	const reader = response.body.getReader();
	while (true) {
	const {done, /** @type {Uint8Array} */ value} = await reader.read();
	const blob = new Blob([value]);
	const url = URL.createObjectURL(blob)
	new Promise(resolve => setTimeout(resolve, 1000)).then(() => URL.revokeObjectURL(url));
	port.postMessage({
	done,
	value: url,
	i: i++
	});
	if (done) {
	break;
	}
	}
	}
	});
	let resolve;
	let promise;
	function updatePromise() {
	promise = new Promise(_resolve => {
	resolve = _resolve;
	});
	}
	updatePromise();


	const port = chrome.runtime.connect({name: "demo-fetch"});
	port.onMessage.addListener(async function({done, value, i}) {
	console.log({done, value, i});
	const ab = await fetch(value).then(r => r.arrayBuffer());
	const u8a = new Uint8Array(ab);

	console.log(i, u8a);
	resolve({done, value: u8a, i});
	updatePromise();
	});

	console.log("Create ReadableStream");
	try {
	rs = new ReadableStream({
	async start(controller) {
	while (true) {
	const {done, value} = await promise;
	if (done) {
	break;
	}
	controller.enqueue(value);
	}
	controller.close();
	}
	});
	} catch (e) {
	console.error(e);
	}
	console.log("ReadableStream is created", rs);

	new Response(rs)
	.blob()
	.then(blob => {
	console.log(blob);
	const a = document.createElement("a");
	a.href = URL.createObjectURL(blob);
	a.download = "GrimGrossKoodoo.mp4";
	a.click();
	new Promise(resolve => setTimeout(resolve, 1000)).then(() => URL.revokeObjectURL(a.href));
	});
	{
	"manifest_version": 2,
	"name": "readable-stream-demo",
	"short_name": "rs-demo",
	"description": "ReadableStream demo extension",
	"version": "1.0",
	"content_scripts": [
	{
	"matches": ["<all_urls>"],
	"js": ["content.js"],
	"run_at": "document_start"
	}
	],
	"background": {
	"page": "background.html",
	"persistent": true
	},
	"permissions": ["<all_urls>", "activeTab", "tabs"]
	}
	{
	"name": "readable-stream-extension-demo",
	"version": "1.0.0",
	"type": "module"
	}