New source found from dndbeyond.com

ddb_main/node_modules/axios/lib/helpers/parseHeaders.js

@@ -1,15 +1,28 @@
 'use strict';
 
-var utils = require('./../utils');
+import utils from '../utils.js';
 
-// Headers whose duplicates are ignored by node
+// RawAxiosHeaders whose duplicates are ignored by node
 // c.f. https://nodejs.org/api/http.html#http_message_headers
-var ignoreDuplicateOf = [
-  'age', 'authorization', 'content-length', 'content-type', 'etag',
-  'expires', 'from', 'host', 'if-modified-since', 'if-unmodified-since',
-  'last-modified', 'location', 'max-forwards', 'proxy-authorization',
-  'referer', 'retry-after', 'user-agent'
-];
+const ignoreDuplicateOf = utils.toObjectSet([
+  'age',
+  'authorization',
+  'content-length',
+  'content-type',
+  'etag',
+  'expires',
+  'from',
+  'host',
+  'if-modified-since',
+  'if-unmodified-since',
+  'last-modified',
+  'location',
+  'max-forwards',
+  'proxy-authorization',
+  'referer',
+  'retry-after',
+  'user-agent',
+]);
 
 /**
  * Parse headers into an object
@@ -21,33 +34,36 @@ var ignoreDuplicateOf = [
  * Transfer-Encoding: chunked
  * ```
  *
- * @param {String} headers Headers needing to be parsed
+ * @param {String} rawHeaders Headers needing to be parsed
+ *
  * @returns {Object} Headers parsed into an object
  */
-module.exports = function parseHeaders(headers) {
-  var parsed = {};
-  var key;
-  var val;
-  var i;
+export default (rawHeaders) => {
+  const parsed = {};
+  let key;
+  let val;
+  let i;
 
-  if (!headers) { return parsed; }
+  rawHeaders &&
+    rawHeaders.split('\n').forEach(function parser(line) {
+      i = line.indexOf(':');
+      key = line.substring(0, i).trim().toLowerCase();
+      val = line.substring(i + 1).trim();
 
-  utils.forEach(headers.split('\n'), function parser(line) {
-    i = line.indexOf(':');
-    key = utils.trim(line.substr(0, i)).toLowerCase();
-    val = utils.trim(line.substr(i + 1));
-
-    if (key) {
-      if (parsed[key] && ignoreDuplicateOf.indexOf(key) >= 0) {
+      if (!key || (parsed[key] && ignoreDuplicateOf[key])) {
         return;
       }
+
       if (key === 'set-cookie') {
-        parsed[key] = (parsed[key] ? parsed[key] : []).concat([val]);
+        if (parsed[key]) {
+          parsed[key].push(val);
+        } else {
+          parsed[key] = [val];
+        }
       } else {
         parsed[key] = parsed[key] ? parsed[key] + ', ' + val : val;
       }
-    }
-  });
+    });
 
   return parsed;
 };