Impact of Cache-control header as request header

Question

I could see a lot of articles explaining about "Cache-Control" when it is used as a response header. Could somebody explain me what is the impact when we use cache-control as a request header.

Here is the scenario I'm trying to solve.

In the environment I'm working,there is no way I can say not to cache the response in the response header. Everything is fine with this, but one of the requests doesn't need a cached response. This request is a synchronous ajax "GET" request. So,to make it not to use the cache I'm setting "Cache-Control" header in the request the following way.

var xhr = new XMLHTTPRequest();
xhr.open(..,...,false);
xhr.setRequestHeader("Cache-Control","no-cache");
xhr.send(null);

This is returning the response from the cache rather than making an explicit call to server. So how can I make an ajax call that skips the cache?

Answer 1

One common trick is to send a timestamp parameter:

xhr.open(..,... + "?now=" + new Date().getTime(), false);