capabilities.js - used unused variable in merge() (#6935)

- minor update
- the code worked before because Capabilities and
Map both happened to have a keys() function
- added tests in capabilities_test.js

Fixes #6911

javascript/node/selenium-webdriver/lib/capabilities.js

@@ -330,24 +330,22 @@ class Capabilities {
    * @return {!Capabilities} A self reference.
    */
   merge(other) {
-    if (!other) {
-      throw new TypeError('no capabilities provided for merge');
-    }
-
-    let map;
-    if (other instanceof Capabilities) {
-      map = other.map_;
-    } else if (other instanceof Map) {
-      map = other;
+    if (other) {
+      let otherMap;
+      if (other instanceof Capabilities) {
+        otherMap = other.map_;
+      } else if (other instanceof Map) {
+        otherMap = other;
+      } else {
+        otherMap = toMap(other);
+      }
+      otherMap.forEach((value, key) => {
+        this.set(key, value);
+      });
+      return this;
     } else {
-      other = toMap(other);
-    }
-
-    for (let key of other.keys()) {
-      this.set(key, other.get(key));
+      throw new TypeError('no capabilities provided for merge');
     }
-
-    return this;
   }
 
   /**

javascript/node/selenium-webdriver/test/lib/capabilities_test.js

@@ -43,12 +43,12 @@ describe('Capabilities', function() {
   });
 
   it('can merge capabilities', function() {
-    let caps1 = new Capabilities()
-        .set('foo', 'bar')
-        .set('color', 'red');
+    const caps1 = new Capabilities()
+      .set('foo', 'bar')
+      .set('color', 'red');
 
-    let caps2 = new Capabilities()
-        .set('color', 'green');
+    const caps2 = new Capabilities()
+      .set('color', 'green');
 
     assert.equal('bar', caps1.get('foo'));
     assert.equal('red', caps1.get('color'));
@@ -60,6 +60,24 @@ describe('Capabilities', function() {
     assert.equal('red', caps1.get('color'));
     assert.equal('red', caps2.get('color'));
     assert.equal('bar', caps2.get('foo'));
+
+    const caps3 = new Map()
+      .set('color', 'blue');
+
+    caps2.merge(caps3);
+    assert.equal('blue', caps2.get('color'));
+    assert.equal('bar', caps2.get('foo'));
+
+    const caps4 = {foo: 'baz'};
+
+    const caps5 = caps2.merge(caps4);
+
+    assert.equal('blue', caps2.get('color'));
+    assert.equal('baz', caps2.get('foo'));
+    assert.equal('blue', caps5.get('color'));
+    assert.equal('baz', caps5.get('foo'));
+    assert.equal(true, caps5 instanceof Capabilities);
+    assert.equal(caps2, caps5);
   });
 
   it('can be initialized from a hash object', function() {