Move internal modules to “internal” folder.

.internal/hasUnicode.js

@@ -0,0 +1,26 @@
+/** Used to compose unicode character classes. */
+const rsAstralRange = '\\ud800-\\udfff';
+const rsComboMarksRange = '\\u0300-\\u036f';
+const reComboHalfMarksRange = '\\ufe20-\\ufe2f';
+const rsComboSymbolsRange = '\\u20d0-\\u20ff';
+const rsComboRange = rsComboMarksRange + reComboHalfMarksRange + rsComboSymbolsRange;
+const rsVarRange = '\\ufe0e\\ufe0f';
+
+/** Used to compose unicode capture groups. */
+const rsZWJ = '\\u200d';
+
+/** Used to detect strings with [zero-width joiners or code points from the astral planes](http://eev.ee/blog/2015/09/12/dark-corners-of-unicode/). */
+const reHasUnicode = RegExp(`[${ rsZWJ + rsAstralRange + rsComboRange + rsVarRange }]`);
+
+/**
+ * Checks if `string` contains Unicode symbols.
+ *
+ * @private
+ * @param {string} string The string to inspect.
+ * @returns {boolean} Returns `true` if a symbol is found, else `false`.
+ */
+function hasUnicode(string) {
+  return reHasUnicode.test(string);
+}
+
+export default hasUnicode;