Decode base64 encoded gzipped string in Javascript

b64zip.js

const decodePart = async function(data) {
    const ds = new DecompressionStream("gzip");
    const resp = await fetch(`data:application/octet-stream;base64,${data}`);
    const blob = await resp.blob();
    return new Response(blob.stream().pipeThrough(ds)).text();
}

const decodeLine = async function(line) {
    const GzipCompressionMagicHeader = 'H4sI';
    for (const part of line.split(',')) {
        if (part.startsWith(GzipCompressionMagicHeader)) {
            console.log(await decodePart(split));
        }
    }
}