My current issue involves using JavaScript to load a zip file, but no matter what I try, caching the zip file seems impossible. The request header consistently includes a "no-cache" specification in Pragma and Cache-Control, even though I am not adding these myself - it is something being done by the browser (specifically Chrome and Firefox).
I attempted to address this by including http_request.setRequestHeader("Cache-Control", "Public") just before calling http_request.send, which does work momentarily as "Public" shows up in the header. However, this setting gets immediately overridden to "Public, no-cache".
What can be done to bypass or override this automatic behavior? Please exclude solutions involving jQuery! I specifically need guidance on how to achieve this using XMLHttpRequest.