Accessing the web page's HTTP Headers in JavaScript

Question

How do I access a page\'s HTTP response headers via JavaScript?

Related to this question, which was modified to ask about accessing two specific HTTP headers.

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Answer 1

Allain Lalonde's link made my day. Just adding some simple working html code here.
Works with any reasonable browser since ages plus IE9+ and Presto-Opera 12.

All Response Headers with XHR

Note: You get headers of a second request, the result may differ from the initial request.

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Another way
is the more modern fetch() API
https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
Per caniuse.com it's supported by Firefox 40, Chrome 42, Edge 14, Safari 11
Working example code:

All Response Headers with fetch()