Move internal modules to “internal” folder.

.internal/createBaseFor.js

@@ -0,0 +1,26 @@
+/**
+ * Creates a base function for methods like `forIn` and `forOwn`.
+ *
+ * @private
+ * @param {boolean} [fromRight] Specify iterating from right to left.
+ * @returns {Function} Returns the new base function.
+ */
+function createBaseFor(fromRight) {
+  return (object, iteratee, keysFunc) => {
+    const iterable = Object(object);
+    const props = keysFunc(object);
+
+    let index = -1;
+    let length = props.length;
+
+    while (length--) {
+      const key = props[fromRight ? length : ++index];
+      if (iteratee(iterable[key], key, iterable) === false) {
+        break;
+      }
+    }
+    return object;
+  };
+}
+
+export default createBaseFor;