perf: cache defineGetter

lib/request.js

@@ -225,7 +225,7 @@ defineGetter(req, 'query', function query(){
   var querystring = parse(this).query;
 
   return queryparse(querystring);
-});
+}, true);
 
 /**
  * Check if the incoming request contains the "Content-Type"
@@ -299,7 +299,7 @@ defineGetter(req, 'protocol', function protocol(){
   return index !== -1
     ? header.substring(0, index).trim()
     : header.trim()
-});
+}, true);
 
 /**
  * Short-hand for:
@@ -312,7 +312,7 @@ defineGetter(req, 'protocol', function protocol(){
 
 defineGetter(req, 'secure', function secure(){
   return this.protocol === 'https';
-});
+}, true);
 
 /**
  * Return the remote address from the trusted proxy.
@@ -327,7 +327,7 @@ defineGetter(req, 'secure', function secure(){
 defineGetter(req, 'ip', function ip(){
   var trust = this.app.get('trust proxy fn');
   return proxyaddr(this, trust);
-});
+}, true);
 
 /**
  * When "trust proxy" is set, trusted proxy addresses + client.
@@ -350,7 +350,7 @@ defineGetter(req, 'ips', function ips() {
   addrs.reverse().pop()
 
   return addrs
-});
+}, true);
 
 /**
  * Return subdomains as an array.
@@ -378,7 +378,7 @@ defineGetter(req, 'subdomains', function subdomains() {
     : [hostname];
 
   return subdomains.slice(offset);
-});
+}, true);
 
 /**
  * Short-hand for `url.parse(req.url).pathname`.
@@ -389,7 +389,7 @@ defineGetter(req, 'subdomains', function subdomains() {
 
 defineGetter(req, 'path', function path() {
   return parse(this).pathname;
-});
+}, true);
 
 /**
  * Parse the "Host" header field to a host.
@@ -415,7 +415,7 @@ defineGetter(req, 'host', function host(){
   }
 
   return val || undefined;
-});
+}, true);
 
 /**
  * Parse the "Host" header field to a hostname.
@@ -442,7 +442,7 @@ defineGetter(req, 'hostname', function hostname(){
   return index !== -1
     ? host.substring(0, index)
     : host;
-});
+}, true);
 
 /**
  * Check if the request is fresh, aka
@@ -470,7 +470,7 @@ defineGetter(req, 'fresh', function(){
   }
 
   return false;
-});
+}, true);
 
 /**
  * Check if the request is stale, aka
@@ -483,7 +483,7 @@ defineGetter(req, 'fresh', function(){
 
 defineGetter(req, 'stale', function stale(){
   return !this.fresh;
-});
+}, true);
 
 /**
  * Check if the request was an _XMLHttpRequest_.
@@ -495,20 +495,34 @@ defineGetter(req, 'stale', function stale(){
 defineGetter(req, 'xhr', function xhr(){
   var val = this.get('X-Requested-With') || '';
   return val.toLowerCase() === 'xmlhttprequest';
-});
+}, true);
 
 /**
  * Helper function for creating a getter on an object.
  *
- * @param {Object} obj
- * @param {String} name
- * @param {Function} getter
+ * @param {Object} obj - The object to define the property on.
+ * @param {String} name - The name of the property.
+ * @param {Function} getter - The function to call to get the value.
+ * @param {boolean} enableCache - Whether to cache the value.
  * @private
  */
-function defineGetter(obj, name, getter) {
+function defineGetter(obj, name, getter, enableCache) {
+  let cache;
+  let cacheValid = false;
+
   Object.defineProperty(obj, name, {
     configurable: true,
     enumerable: true,
-    get: getter
+    get: function () {
+      if (!enableCache || !cacheValid) {
+        cache = getter.call(this);
+        cacheValid = true;
+      }
+      return cache;
+    },
+    set: function (value) {
+      cache = value;
+      cacheValid = true;
+    }
   });
 }