Move internal modules to “internal” folder.

.internal/baseFilter.js

@@ -0,0 +1,21 @@
+import baseEach from './.internal/baseEach.js';
+
+/**
+ * The base implementation of `filter`.
+ *
+ * @private
+ * @param {Array|Object} collection The collection to iterate over.
+ * @param {Function} predicate The function invoked per iteration.
+ * @returns {Array} Returns the new filtered array.
+ */
+function baseFilter(collection, predicate) {
+  const result = [];
+  baseEach(collection, (value, index, collection) => {
+    if (predicate(value, index, collection)) {
+      result.push(value);
+    }
+  });
+  return result;
+}
+
+export default baseFilter;