Event handler closure scope exposure in jQuery delegated events

Event Handler Closure Scope Exposure in jQuery Delegated Events

jQuery's .on() method enables event delegation by binding handlers to parent elements, which respond to events from matching child elements. Handlers registered this way retain access to their closure scope, including variables or application state captured at registration time.

jQuery provides no built-in mechanism to restrict handler visibility or prevent external invocation, so any code holding a reference to the handler can execute it with full access to that closure. Delegated handlers can also remain active after their associated child elements are removed, as long as the parent persists, which raises concerns about unexpected execution paths and memory retention.

Assume jQuery 3.x with a single shared instance across multiple components.

Which patterns can encapsulate delegated event handlers so internal application state is not accidentally exposed to public invocation? How can scope isolation be verified in practice, for example from the browser console? Does behavior differ meaningfully between jQuery 1.x/2.x and 3.x in this regard?