Is it possible to gather the HTTP headers in JavaScript ? This is just a thought of mine after using Firebug for days. In one of the posts I came to know that, it is impossible to find the HTTP headers in JavaScript, whereas in firebug, we can see the response headers (client side)
so my question is can we cache the HTTP headers in JavaScript ?
The HTTP headers aren't available in JavaScript.
However you could use XMLHttpRequest to do a HEAD request to any resource within the same domain:
var xhr = new XMLHttpRequest();
xhr.open('HEAD', '/', true); // Relative path of resource
xhr.onreadystatechange = function() {
if (xhr.readyState === 4) {
console.log(xhr.getAllResponseHeaders());
}
}
xhr.send(null);
The above will return something like this (running it in Firebug on this page):
Server: nginx
Date: Fri, 09 Jul 2010 18:58:30 GMT
Content-Type: text/html; charset=utf-8
Connection: keep-alive
Cache-Control: public, max-age=60
Content-Length: 33273
Content-Encoding: gzip
Expires: Fri, 09 Jul 2010 18:59:31 GMT
Last-Modified: Fri, 09 Jul 2010 18:58:31 GMT
Vary: *
You can easily get the value of single headers like this:
xhr.getResponseHeader('Last-Modified');
Firebug is not a web application - it is a XUL application (that is, a Mozilla application, written with XUL and javascript) and as such has access to http headers that browser side javascript cannot access.
You cannot access http header via javascript in the browser.
