In this article, we will quickly go through how to send files in the response in an Express JS application that can be downloaded and saved by the browser.

Express.js provides a method to send files in the response, so that it gets prompted by the browser and saved to the local disk.

Syntax

res.download(path [, filename] [, options] [, fn])

Sending file without changing the name

res.download("uploads/output.xlsx");

In this case, output.xlsx will be fetched from the uploads directory and will be sent in the response.

Sending the file with new name

By default, the Content-Disposition header “filename=” parameter is path which typically appears in the browser dialog. We can override this default with filename which will be filled in the file download dialog.

res.download("uploads/output.xlsx", "output_for_27th.xlsx");

Handling errors

res.download() method provides a callback to handle errors.

res.download("uploads/output.xlsx", "output_for_27th.xlsx", (err) => {
  if (err) {
    //handle error
    return
  } else {
    //success
  }
});

Sending multiple files

Multiple files can be sent in the response but not individually. We need to pack all the files together as an archive and send it in the response.