Move internal modules to “internal” folder.

.internal/baseHas.js

@@ -0,0 +1,16 @@
+/** Used to check objects for own properties. */
+const hasOwnProperty = Object.prototype.hasOwnProperty;
+
+/**
+ * The base implementation of `has` without support for deep paths.
+ *
+ * @private
+ * @param {Object} [object] The object to query.
+ * @param {Array|string} key The key to check.
+ * @returns {boolean} Returns `true` if `key` exists, else `false`.
+ */
+function baseHas(object, key) {
+  return object != null && hasOwnProperty.call(object, key);
+}
+
+export default baseHas;