# Advanced topics

- [XBL Modes](/xforms/xbl/advanced-topics/modes.md)
- [JavaScript companion classes](/xforms/xbl/advanced-topics/javascript.md)
- [XBL library](/xforms/xbl/advanced-topics/library.md)
- [Extensions](/xforms/xbl/advanced-topics/extensions.md)
- [Attachment controls](/xforms/xbl/advanced-topics/attachments.md)