Parses the response from XmlHttpRequest.getAllResponseHeaders() into a key/value pair.

gistfile1.js

/**
 * XmlHttpRequest's getAllResponseHeaders() method returns a string of response
 * headers according to the format described here:
 * http://www.w3.org/TR/XMLHttpRequest/#the-getallresponseheaders-method
 * This method parses that string into a user-friendly key/value pair object.
 */
function parseResponseHeaders(headerStr) {
  var headers = {};
  if (!headerStr) {
    return headers;
  }
  var headerPairs = headerStr.split('\u000d\u000a');
  for (var i = 0; i < headerPairs.length; i++) {
    var headerPair = headerPairs[i];
    // Can't use split() here because it does the wrong thing
    // if the header value has the string ": " in it.
    var index = headerPair.indexOf('\u003a\u0020');
    if (index > 0) {
      var key = headerPair.substring(0, index);
      var val = headerPair.substring(index + 2);
      headers[key] = val;
    }
  }
  return headers;
}

No license is always proper to use right? I don't really think Monsur would mind if you would use this :p

Here's my solution:

function getHeadersAsObject(xhr)
{
  let headers = {}

  xhr.getAllResponseHeaders()
    .split('\u000d\u000a')
    .forEach((line) => {
      if (line.length > 0)
      {
        let delimiter = '\u003a\u0020',
          header = line.split(delimiter)

        headers[header.shift().toLowerCase()] = header.join(delimiter)
      }
    })

  return headers
}

This work is dedicated to the public domain.

function parseResponseHeaders(headerStr) {
    return Object.fromEntries(
        (headerStr || '').split('\u000d\u000a') // '\n'
            .map(line => line.split('\u003a\u0020')) // ": "
            .filter(pair => pair[0] !== undefined && pair[1] !== undefined)
    );
}