in javascript how can I detect if a browser will display or download a pdf?

Question

Say I have:

• a webpage with an iframe: <iframe src="" style="display:none;"></iframe>

• an URL pointing to a PDF document: http://www.example.com

• some javascript that will do iframe.src = pdfurl

• a button that will trigger such javascript

• if the browser is going to display the PDF inline, the button will say "view pdf" and when clicked will make the iframe visible

• otherwise it will say "download pdf"

I found a way to detect whether the pdf has been loaded in the iframe: reading iframe.contentDocument.contentType after onload has fired, but

• this won't allow me to display the correct button
• onload does not fire if the file is being downloaded

Thanks :)

Answer 1

To tell the client's browser to download a response as a file, set the Content-Disposition HTTP header to 'attachment' in your response. This is no guarantee, but it's the proper method of telling the browser how to handle the content.