Should i call "zip.end()" with ondata finish === true?

[crapthings]

export function downloadAsZip (filename, downloads) {
  const fileStream = streamSaver.createWriteStream(`${filename}.zip`);
  const writer = fileStream.getWriter();
  const zip = new fflate.Zip();
  zip.ondata = writeStreamForDownload;

  downloads?.forEach(({ filename, downloadUrl }) => fetch(downloadUrl).then(pipeZipfile(filename)));

  function writeStreamForDownload (err, chunk, finish) {
    writer.write(chunk);
    if (err || finish) {
      return writer.close();
    }
  };

  function pipeZipfile (filename) {
    return async function (response) {
      const file = new fflate.ZipPassThrough(filename);
      zip.add(file);
      const reader = response.body.getReader();
      while (true) {
        const { done, value } = await reader.read();
        if (done) {
          file.push(new Uint8Array(0), true);
          break;
        }
        file.push(value);
      };
      zip.end();
    };
  };
};

i can get proper zip file by these code, but i don't know why i put zip.end into a forEach loop it still works

[101arrowz]

This only works because of the delay in the data arrival; you shouldn't use this solution. Instead, call zip.end() one time after you have called zip.add() with every file you need. You also have to make sure you don't call accidentally call zip.add() after zip.end(), e.g. if you put the add() calls into the event loop with async/await. Try this:

export function downloadAsZip (filename, downloads) {
  const fileStream = streamSaver.createWriteStream(`${filename}.zip`);
  const writer = fileStream.getWriter();
  const zip = new fflate.Zip();
  zip.ondata = writeStreamForDownload;
  downloads?.forEach(({ filename, downloadUrl }) => fetch(downloadUrl).then(pipeZipfile(filename)));
  // Now all the zip.add() calls executed synchronously, so this is safe to call
  zip.end();

  function writeStreamForDownload (err, chunk, finish) {
    writer.write(chunk);
    if (err || finish) {
      return writer.close();
    }
  };

  function pipeZipfile (filename) {
    // I moved this out of the async function so it executes synchronously
    const file = new fflate.ZipPassThrough(filename);
    zip.add(file);
    return async function (response) {
      const reader = response.body.getReader();
      while (true) {
        const { done, value } = await reader.read();
        if (done) {
          file.push(new Uint8Array(0), true);
          break;
        }
        file.push(value);
      };
    };
  };
};

[crapthings]

amazing~