Move internal modules to “internal” folder.

.internal/baseSortedUniq.js

@@ -0,0 +1,29 @@
+import eq from './eq.js';
+
+/**
+ * The base implementation of `sortedUniq` and `sortedUniqBy`.
+ *
+ * @private
+ * @param {Array} array The array to inspect.
+ * @param {Function} [iteratee] The iteratee invoked per element.
+ * @returns {Array} Returns the new duplicate free array.
+ */
+function baseSortedUniq(array, iteratee) {
+  let seen;
+  let index = -1;
+  let resIndex = 0;
+
+  const length = array.length;
+  const result = [];
+
+  while (++index < length) {
+    const value = array[index], computed = iteratee ? iteratee(value) : value;
+    if (!index || !eq(computed, seen)) {
+      seen = computed;
+      result[resIndex++] = value === 0 ? 0 : value;
+    }
+  }
+  return result;
+}
+
+export default baseSortedUniq;