http: switch on string values

Long ago, V8 was much faster switching on string lengths than values.
That is no longer the case, so we can simplify a couple of methods.

PR-URL: https://github.com/nodejs/node/pull/18351
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Kyle Farnung <kfarnung@microsoft.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>

benchmark/http/set_header.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const common = require('../common.js');
+const { OutgoingMessage } = require('_http_outgoing');
+
+const bench = common.createBenchmark(main, {
+  value: [
+    'X-Powered-By',
+    'Vary',
+    'Set-Cookie',
+    'Content-Type',
+    'Content-Length',
+    'Connection',
+    'Transfer-Encoding'
+  ],
+  n: [1e6],
+});
+
+function main(conf) {
+  const n = +conf.n;
+  const value = conf.value;
+
+  const og = new OutgoingMessage();
+
+  bench.start();
+  for (var i = 0; i < n; i++) {
+    og.setHeader(value, '');
+  }
+  bench.end(n);
+}

lib/_http_outgoing.js

@@ -510,18 +510,15 @@ OutgoingMessage.prototype.setHeader = function setHeader(name, value) {
   const key = name.toLowerCase();
   this[outHeadersKey][key] = [name, value];
 
-  switch (key.length) {
+  switch (key) {
-    case 10:
+    case 'connection':
-      if (key === 'connection')
+      this._removedConnection = false;
-        this._removedConnection = false;
       break;
-    case 14:
+    case 'content-length':
-      if (key === 'content-length')
+      this._removedContLen = false;
-        this._removedContLen = false;
       break;
-    case 17:
+    case 'transfer-encoding':
-      if (key === 'transfer-encoding')
+      this._removedTE = false;
-        this._removedTE = false;
       break;
   }
 };
@@ -583,22 +580,18 @@ OutgoingMessage.prototype.removeHeader = function removeHeader(name) {
 
   var key = name.toLowerCase();
 
-  switch (key.length) {
+  switch (key) {
-    case 10:
+    case 'connection':
-      if (key === 'connection')
+      this._removedConnection = true;
-        this._removedConnection = true;
       break;
-    case 14:
+    case 'content-length':
-      if (key === 'content-length')
+      this._removedContLen = true;
-        this._removedContLen = true;
       break;
-    case 17:
+    case 'transfer-encoding':
-      if (key === 'transfer-encoding')
+      this._removedTE = true;
-        this._removedTE = true;
       break;
-    case 4:
+    case 'date':
-      if (key === 'date')
+      this.sendDate = false;
-        this.sendDate = false;
       break;
   }