R2 implements an S3 API and a Workers binding

curl -X PUT <cool-presigned-url> --data-binary 'lol' --header 'If-None-Match: "9cdfb439c7876e703e307864c9167a15"' -vvv

try {
    for (const file of files) {
        const fileStream = fs.readFileSync(file);
        const fileName = file.replace(/uploads\//g, '');

        console.log(fileName)

        const uploadParams: PutObjectCommandInput = {
            Bucket: 'test-bucket',
            Key: fileName,
            Body: fileStream,
            ContentLength: fs.statSync(file).size,
            ContentType: 'application/octet-stream'
        };

        const data = await S3.send(new PutObjectCommand(uploadParams));
        console.log("Success", data);
    }
} catch (err) {
    console.log("Error", err);
}

const body = 'lol';
const digest = createHash('md5').update(body).digest("hex");

const cmd = new PutObjectCommand({Bucket: 'sdk-example', Key: 'dog.png', Body: body});

cmd.middlewareStack.add((next, context) => async (args) => {
    args.request.headers["if-none-match"] = `"${digest}"`;
    const result = await next(args);
    return result;
}, {
    step: "build",
    name: "addETag"
})

const data = await S3.send(cmd);
console.log(data);