Fixes request headers to conform to spec more closely.

I've made the request headers case insensitive for setting and getting by creating a mapping hash to map the insensitive names with the ones used in setting. I've also fixed setRequestHeader to append values to existing ones as per the spec. Because of this I needed to set the defaults on send if they haven't been set previously (user-agent obviously can't because it's in the restricted list).

Author: jacwright

lib/XMLHttpRequest.js

@@ -40,7 +40,8 @@ exports.XMLHttpRequest = function() {
     "Accept": "*/*",
   };
 
-  var headers = defaultHeaders;
+  var headers = {};
+  var headersCase = {};
 
   // These headers are not user setable.
   // The following are allowed but banned in the spec:
@@ -177,7 +178,7 @@ exports.XMLHttpRequest = function() {
   };
 
   /**
-   * Sets a header for the request.
+   * Sets a header for the request or appends the value if one is already set.
    *
    * @param string header Header name
    * @param string value Header value
@@ -193,7 +194,9 @@ exports.XMLHttpRequest = function() {
     if (sendFlag) {
       throw "INVALID_STATE_ERR: send flag is true";
     }
-    headers[header] = value;
+    header = headersCase[header.toLowerCase()] || header;
+    headersCase[header.toLowerCase()] = header;
+    headers[header] = headers[header] ? headers[header] + ', ' + value : value;
   };
 
   /**
@@ -243,9 +246,8 @@ exports.XMLHttpRequest = function() {
    * @return string Returns the request header or empty string if not set
    */
   this.getRequestHeader = function(name) {
-    // @TODO Make this case insensitive
-    if (typeof name === "string" && headers[name]) {
-      return headers[name];
+    if (typeof name === "string" && headersCase[name.toLowerCase()]) {
+      return headers[headersCase[name.toLowerCase()]];
     }
 
     return "";
@@ -325,6 +327,13 @@ exports.XMLHttpRequest = function() {
     // Add query string if one is used
     var uri = url.pathname + (url.search ? url.search : '');
 
+    // Set the defaults if they haven't been set
+    for (var name in defaultHeaders) {
+      if (!headersCase[name.toLowerCase()]) {
+        headers[name] = defaultHeaders[name];
+      }
+    }
+
     // Set the Host header or the server may reject the request
     headers["Host"] = host;
     if (!((ssl && port === 443) || port === 80)) {