url: improve resolveObject with ObjectAssign

lib/url.js

@@ -24,6 +24,7 @@
 const {
   Boolean,
   Int8Array,
+  ObjectAssign,
   ObjectKeys,
   StringPrototypeCharCodeAt,
   decodeURIComponent,
@@ -735,11 +736,7 @@ Url.prototype.resolveObject = function resolveObject(relative) {
   }
 
   const result = new Url();
-  const tkeys = ObjectKeys(this);
-  for (let tk = 0; tk < tkeys.length; tk++) {
-    const tkey = tkeys[tk];
-    result[tkey] = this[tkey];
-  }
+  ObjectAssign(result, this);
 
   // Hash is always overridden, no matter what.
   // even href="" will remove it.
@@ -754,12 +751,13 @@ Url.prototype.resolveObject = function resolveObject(relative) {
   // Hrefs like //foo/bar always cut to the protocol.
   if (relative.slashes && !relative.protocol) {
     // Take everything except the protocol from relative
-    const rkeys = ObjectKeys(relative);
-    for (let rk = 0; rk < rkeys.length; rk++) {
-      const rkey = rkeys[rk];
-      if (rkey !== 'protocol')
-        result[rkey] = relative[rkey];
-    }
+    const relativeWithoutProtocol = ObjectKeys(relative).reduce((acc, key) => {
+      if (key !== 'protocol') {
+        acc[key] = relative[key];
+      }
+      return acc;
+    }, {});
+    ObjectAssign(result, relativeWithoutProtocol);
 
     // urlParse appends trailing / to urls like http://www.example.com
     if (slashedProtocol.has(result.protocol) &&
@@ -781,11 +779,7 @@ Url.prototype.resolveObject = function resolveObject(relative) {
     // because that's known to be hostless.
     // anything else is assumed to be absolute.
     if (!slashedProtocol.has(relative.protocol)) {
-      const keys = ObjectKeys(relative);
-      for (let v = 0; v < keys.length; v++) {
-        const k = keys[v];
-        result[k] = relative[k];
-      }
+      ObjectAssign(result, relative);
       result.href = result.format();
       return result;
     }