Callbacks

Callbacks is a typed event registry with support for one-time listeners, protected listeners, and delayed execution.

It is used internally by Module and all components. You can also instantiate it directly when building custom logic.

Event map

Define events by extending ICallbacksMap. Each key is an event name; the value is the payload type passed to listeners on emit. Use undefined for events without a payload.

interface IMyCallbacks extends ICallbacksMap {
  init: undefined;
  update: { value: number };
}

In components

Every Module owns a callbacks instance. Component constructor props such as onMove or onDestroy are registered on that instance (onMove → move).

You can subscribe in two ways:

• Declarative — pass onEvent functions in constructor props.
• Imperative — call instance.on('event', listener) after creation.

Both approaches use the same underlying Callbacks instance. See Module for the component-level API.

Constructor

new Callbacks<Types, Ctx>(props?)

Option	Type	Description
ctx	Ctx	Optional context forwarded as the second argument to every listener

Inside components, ctx is the module instance (this).

Listener signature

Every listener receives two arguments:

(data, ctx) => void

• data — event payload from the map (undefined is passed explicitly when the event has no payload).
• ctx — value from constructor ctx (the module instance in components).

Methods

Method	Returns	Description
on(target, fn, settings?)	() => void	Registers a listener. Returned function removes it.
add(target, fn, settings?)	{ id, remove }	Same as on, but also exposes the callback id for remove().
emit(target, arg)	void	Invokes all listeners for the event.
remove(id)	boolean	Removes a listener by id. Protected listeners are skipped.
destroy()	void	Clears all listeners. Further calls to on / add are no-ops.
list	ICallback[]	Snapshot of registered listeners (for debugging).

Prefer on() when you only need a destructor. Use add() when you need the callback id.

Settings

Pass as the third argument to on() or add():

Option	Type	Default	Description
once	boolean	false	Remove the listener after the first execution.
protected	boolean	false	Prevent manual removal via remove() or the on() destructor. Cleared on destroy().
timeout	number	undefined	Delay before the listener runs, in milliseconds.
name	string	undefined	Optional label for debugging (list).

Example

import { Callbacks, ICallbacksMap } from 'vevet';

interface IMyCallbacks extends ICallbacksMap {
  init: undefined;
  update: { value: number };
}

const callbacks = new Callbacks<IMyCallbacks>();

const remove = callbacks.on('update', ({ value }) => {
  console.log(value);
});

callbacks.emit('update', { value: 1 });

remove();
callbacks.destroy();

Typedoc

For full API details and types, see Callbacks in Typedoc.