Ensure _.has treats sparse arrays as dense.

lodash.src.js

@@ -9715,13 +9715,18 @@
         return false;
       }
       var result = hasOwnProperty.call(object, path);
-      if (!result && !isKey(path)) {
-        path = toPath(path);
-        object = path.length == 1 ? object : baseGet(object, baseSlice(path, 0, -1));
-        path = last(path);
-        result = object != null && hasOwnProperty.call(object, path);
+      if (result) {
+        return result;
       }
-      return result || (lodash.support.nonEnumStrings && isString(object) && isIndex(path, object.length));
+      if (isKey(path)) {
+        var length = object.length;
+        return isLength(length) &&
+          (isArray(object) || (support.nonEnumStrings && isString(object)) ||
+            (support.nonEnumArgs && isArguments(object))) && isIndex(path, length);
+      }
+      path = toPath(path);
+      object = path.length == 1 ? object : baseGet(object, baseSlice(path, 0, -1));
+      return object != null && hasOwnProperty.call(object, last(path));
     }
 
     /**

test/test.js

@@ -6248,6 +6248,8 @@
   QUnit.module('lodash.has');
 
   (function() {
+    var args = arguments;
+
     test('should check for own properties', 2, function() {
       var object = { 'a': 1 };
 
@@ -6311,6 +6313,14 @@
       });
     });
 
+    test('should treat sparse arrays as dense', 1, function() {
+      strictEqual(_.has(Array(1), 0), true);
+    });
+
+    test('should work with `arguments` objects', 1, function() {
+      strictEqual(_.has(args, 1), true);
+    });
+
     test('should check for a key over a path', 2, function() {
       var object = { 'a.b.c': 3, 'a': { 'b': { 'c': 4 } } };
 
@@ -6352,7 +6362,7 @@
         strictEqual(_.has(object, path), false);
       });
     });
-  }());
+  }(1, 2, 3));
 
   /*--------------------------------------------------------------------------*/