http: improve for-loop readability in _http_outgoing.js

PR-URL: #26408
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/_http_outgoing.js

@@ -295,21 +295,21 @@ function _storeHeader(firstLine, headers) {
     header: firstLine
   };
 
-  var key;
-  if (headers === this[outHeadersKey]) {
-    for (key in headers) {
-      const entry = headers[key];
-      processHeader(this, state, entry[0], entry[1], false);
-    }
-  } else if (Array.isArray(headers)) {
-    for (var i = 0; i < headers.length; i++) {
-      const entry = headers[i];
-      processHeader(this, state, entry[0], entry[1], true);
-    }
-  } else if (headers) {
-    for (key in headers) {
-      if (hasOwnProperty(headers, key)) {
-        processHeader(this, state, key, headers[key], true);
+  if (headers) {
+    if (headers === this[outHeadersKey]) {
+      for (const key in headers) {
+        const entry = headers[key];
+        processHeader(this, state, entry[0], entry[1], false);
+      }
+    } else if (Array.isArray(headers)) {
+      for (const entry of headers) {
+        processHeader(this, state, entry[0], entry[1], true);
+      }
+    } else {
+      for (const key in headers) {
+        if (hasOwnProperty(headers, key)) {
+          processHeader(this, state, key, headers[key], true);
+        }
       }
     }
   }