Techniques are disclosed for event-based architectures for implementing expand-collapse input-output operations in user interfaces. Certain techniques are disclosed herein that allow for a expand and/or collapse functionality via passing asynchronous events to a datasource module, which may or may not be routed through a view module. The datasource module determines what data is to be shown or hidden and issues an insert/delete event back to the view module. The insert/delete event may include additional data to be inserted into the user interface, and may include an identifier of where, within the displayed user interface, data is to be inserted or deleted. A view module may be configured to receive insert or delete events, and, in response, cause the user interface to be modified based upon the event. The view module may perform these updates by inserting or removing Document Object Model (DOM) nodes from a DOM associated with the user interface.