http: avoid using object for removed header status

PR-URL: https://github.com/nodejs/node/pull/10558
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

lib/_http_outgoing.js

@@ -13,14 +13,6 @@ const checkInvalidHeaderChar = common._checkInvalidHeaderChar;
 const CRLF = common.CRLF;
 const debug = common.debug;
 
-
-const automaticHeaders = {
-  connection: true,
-  'content-length': true,
-  'transfer-encoding': true,
-  date: true
-};
-
 var RE_FIELDS = new RegExp('^(?:Connection|Transfer-Encoding|Content-Length|' +
                            'Date|Expect|Trailer|Upgrade)$', 'i');
 var RE_CONN_VALUES = /(?:^|\W)close|upgrade(?:$|\W)/ig;
@@ -64,7 +56,9 @@ function OutgoingMessage() {
   this.shouldKeepAlive = true;
   this.useChunkedEncodingByDefault = true;
   this.sendDate = false;
-  this._removedHeader = {};
+  this._removedConnection = false;
+  this._removedContLen = false;
+  this._removedTE = false;
 
   this._contentLength = null;
   this._hasBody = true;
@@ -279,7 +273,7 @@ function _storeHeader(firstLine, headers) {
   }
 
   // keep-alive logic
-  if (this._removedHeader.connection) {
+  if (this._removedConnection) {
     this._last = true;
     this.shouldKeepAlive = false;
   } else if (!state.connection) {
@@ -300,11 +294,11 @@ function _storeHeader(firstLine, headers) {
     } else if (!this.useChunkedEncodingByDefault) {
       this._last = true;
     } else {
-          !this._removedHeader['content-length'] &&
       if (!state.trailer &&
+          !this._removedContLen &&
           typeof this._contentLength === 'number') {
-      } else if (!this._removedHeader['transfer-encoding']) {
         state.header += 'Content-Length: ' + this._contentLength + CRLF;
+      } else if (!this._removedTE) {
         state.header += 'Transfer-Encoding: chunked\r\n';
         this.chunkedEncoding = true;
       } else {
@@ -405,8 +399,20 @@ OutgoingMessage.prototype.setHeader = function setHeader(name, value) {
   const key = name.toLowerCase();
   this._headers[key] = [name, value];
 
-  if (automaticHeaders[key])
+  switch (key.length) {
-    this._removedHeader[key] = false;
+    case 10:
+      if (key === 'connection')
+        this._removedConnection = false;
+      break;
+    case 14:
+      if (key === 'content-length')
+        this._removedContLen = false;
+      break;
+    case 17:
+      if (key === 'transfer-encoding')
+        this._removedTE = false;
+      break;
+  }
 };
 
 
@@ -435,10 +441,24 @@ OutgoingMessage.prototype.removeHeader = function removeHeader(name) {
 
   var key = name.toLowerCase();
 
+  switch (key.length) {
+    case 10:
+      if (key === 'connection')
+        this._removedConnection = true;
+      break;
+    case 14:
+      if (key === 'content-length')
+        this._removedContLen = true;
+      break;
+    case 17:
+      if (key === 'transfer-encoding')
+        this._removedTE = true;
+      break;
+    case 4:
       if (key === 'date')
         this.sendDate = false;
-  else if (automaticHeaders[key])
+      break;
-    this._removedHeader[key] = true;
+  }
 
   if (this._headers) {
     delete this._headers[key];