--- /dev/null
+'use strict';
+var charAt = require('../internals/string-multibyte').charAt;
+
+// `AdvanceStringIndex` abstract operation
+// https://tc39.github.io/ecma262/#sec-advancestringindex
+module.exports = function (S, index, unicode) {
+ return index + (unicode ? charAt(S, index).length : 1);
+};