QTBUG-52612

--- src/qml/qml/v8/qqmlbuiltinfunctions.cpp
+++ src/qml/qml/v8/qqmlbuiltinfunctions.cpp
@@ -98,6 +98,12 @@ Heap::QtObject::QtObject(QQmlEngine *qmlEngine)
     o->put((str = scope.engine->newString(QStringLiteral("Asynchronous"))), (v = QV4::Primitive::fromInt32(0)));
     o->put((str = scope.engine->newString(QStringLiteral("Synchronous"))), (v = QV4::Primitive::fromInt32(1)));

+    // add enums for atob and btoa
+    o->put((str = scope.engine->newString(QStringLiteral("Base64Encoding"))), (v = QByteArray::Base64Encoding));
+    o->put((str = scope.engine->newString(QStringLiteral("Base64UrlEncoding"))), (v = QByteArray::Base64UrlEncoding));
+    o->put((str = scope.engine->newString(QStringLiteral("KeepTrailingEquals"))), (v = QByteArray::KeepTrailingEquals));
+    o->put((str = scope.engine->newString(QStringLiteral("OmitTrailingEquals"))), (v = QByteArray::OmitTrailingEquals));
+
     o->defineDefaultProperty(QStringLiteral("include"), QV4Include::method_include);
     o->defineDefaultProperty(QStringLiteral("isQtObject"), QV4::QtObject::method_isQtObject);
     o->defineDefaultProperty(QStringLiteral("rgba"), QV4::QtObject::method_rgba);