How would I monitor all http requests coming from a site [Chrome Extension]

Question

I'm currently writing a chrome extension and require to monitor and get a header from a http POST request from a site. How would I wait for a request from the site and then save the specified header's argument to a variable for future use?

Answer 1

I ended up using:

chrome.webRequest.onSendHeaders.addListener(function (details) {
    //my stuff here
}, {
  urls: ["<all_urls>"],
  types: ["main_frame", "sub_frame", "stylesheet", "script", "image", "object", "xmlhttprequest", "other"]
}, ["requestHeaders"]);

along with some code to store the varible i got from details.* .