JavaScript: How to capture user's choice in SaveFileDialog?

Other Questions JavaScript
1

I’m trying to show a SaveFileDialog to users and get their response. Here’s what I’ve got in my Page_Load event:

function showSaveDialog() {
  const filename = 'report_' + Math.random().toString(36).substring(7) + '.pdf';
  const fileContent = generatePdfContent();

  const blob = new Blob([fileContent], { type: 'application/pdf' });
  const link = document.createElement('a');
  link.href = window.URL.createObjectURL(blob);
  link.download = filename;
  link.click();
}

This code creates a PDF file and prompts the user to save it. But I need to know if they actually saved it or cancelled. Is there a way to track the user’s choice?

Also I’m getting a weird error sometimes: ‘Cannot read property of undefined’. Any ideas what might be causing this? Thanks for any help!

2

hey there! unfortunately javascript can’t directly track if the user saved or cancelled the file download due to security reasons. one workaround could be to use a server-side approach or implement a client-side confirmation dialog before triggering the download.

for the error, it might be happening if fileContent is undefined. make sure generatePdfContent() is returning valid data. hope this helps!

3

I’ve encountered similar issues when working with file downloads in JavaScript. One approach I’ve used is to track the download indirectly by setting a flag when the download starts and then using a setTimeout to check if the blob URL still exists after a short delay. If it does, it’s likely the user cancelled.

As for the error, I’ve seen this happen when the PDF generation fails silently. Try adding some console.logs in generatePdfContent() to see where it might be breaking. Also, make sure you’re handling any potential async operations correctly.

A tip from my experience: consider using the FileSaver.js library. It provides a more robust way to handle file saves across different browsers and can simplify your code quite a bit. It’s saved me a lot of headaches in similar situations.

4

Regarding your SaveFileDialog issue, JavaScript’s security model indeed limits direct access to user actions in file dialogs. A potential workaround is to implement a custom UI for file saving, perhaps using the File System Access API if browser support aligns with your needs.

As for the ‘Cannot read property of undefined’ error, it’s likely occurring in the generatePdfContent() function. I’d suggest adding error handling and logging to pinpoint the exact location. Consider wrapping the content generation in a try-catch block and validating the output before creating the Blob.

Lastly, for better user experience, you might want to consider using async/await syntax for smoother execution flow, especially if generatePdfContent() involves any asynchronous operations.