Class: Hooks<Events>

A simple yet effective implementation for registering and executing lifecycle hooks around specific events.

The Hooks class allows you to register hook handlers for different events, execute them, and manage cleanup operations. Hooks can be functions or objects with a handle method.

Example

// Define event types
type AppEvents = {
  saving: [[User], [Error | null, User]];
  deleting: [[User], [Error | null]];
};

const hooks = new Hooks<AppEvents>();

// Add a function handler
hooks.add("saving", function hashPassword(user) {
  user.password = hash(user.password);
});

// Add a handler provider
hooks.add("saving", {
  name: "validateEmail",
  handle(event, user) {
    if (!isValid(user.email)) {
      throw new Error("Invalid email");
    }
  },
});

// Execute hooks
await hooks.runner("saving").run(user);

Type Parameters

Type Parameter	Description
Events extends Record<string, [any[], any[]]>	A record mapping event names to tuples of [HookArgs, CleanupArgs]

Constructors

Constructor

new Hooks<Events>(): Hooks<Events>;

Returns

Hooks<Events>

Methods

add()

add<Event>(event: Event, handler:
  | HookHandler<Events[Event][0], Events[Event][1]>
  | HookHandlerProvider<Events[Event][0], Events[Event][1]>): this;

Add a hook handler for a given event. Adding the same handler twice will result in a noop.

Type Parameters

Type Parameter
Event extends string | number | symbol

Parameters

Parameter	Type	Description
event	Event	The event name to add the handler for
handler	| HookHandler<Events[Event][0], Events[Event][1]> | HookHandlerProvider<Events[Event][0], Events[Event][1]>	The hook handler function or handler provider

Returns

this

Example

const hooks = new Hooks();

// Add a function handler
hooks.add("saving", function hashPassword(user) {
  user.password = hash(user.password);
});

// Add a handler provider
hooks.add("saving", {
  name: "EmailValidator",
  handle(event, user) {
    validateEmail(user.email);
  },
});

---

all()

all(): { [Event in string | number | symbol]: Map<Event, Set<HookHandler<Events[Event][0], Events[Event][1]> | HookHandlerProvider<Events[Event][0], Events[Event][1]>>> }[keyof Events];

Get access to all the registered hooks. The return value is a map of the event name and a set of handlers.

Returns

{ [Event in string | number | symbol]: Map<Event, Set<HookHandler<Events[Event][0], Events[Event][1]> | HookHandlerProvider<Events[Event][0], Events[Event][1]>>> }[keyof Events]

Example

const hooks = new Hooks();
const allHooks = hooks.all();
console.log(allHooks.size); // Number of events with handlers

---

clear()

clear(event?: keyof Events): void;

Clear all the hooks for a specific event or all the events.

Parameters

Parameter	Type	Description
event?	keyof Events	Optional event name to clear hooks for. If not provided, clears all hooks.

Returns

void

Example

const hooks = new Hooks();

// Clear hooks for specific event
hooks.clear("saving");

// Clear all hooks
hooks.clear();

---

has()

has<Event>(event: Event, handler?:
  | HookHandler<Events[Event][0], Events[Event][1]>
  | HookHandlerProvider<Events[Event][0], Events[Event][1]>): boolean;

Find if a handler for a given event exists.

Type Parameters

Type Parameter
Event extends string | number | symbol

Parameters

Parameter	Type	Description
event	Event	The event name to check
handler?	| HookHandler<Events[Event][0], Events[Event][1]> | HookHandlerProvider<Events[Event][0], Events[Event][1]>	Optional specific handler to check for

Returns

boolean

Example

const hooks = new Hooks();

// Check if any handlers exist for an event
if (hooks.has("saving")) {
  console.log("Saving hooks are registered");
}

// Check if specific handler exists
if (hooks.has("saving", hashPasswordHandler)) {
  console.log("Hash password handler is registered");
}

---

merge()

merge(hooks: Hooks<Events>): void;

Merge hooks from an existing hooks instance.

Parameters

Parameter	Type	Description
hooks	Hooks<Events>	The hooks instance to merge from

Returns

void

Example

const hooks1 = new Hooks();
const hooks2 = new Hooks();

hooks2.add("saving", handler1);
hooks2.add("deleting", handler2);

// Merge hooks2 into hooks1
hooks1.merge(hooks2);

---

remove()

remove<Event>(event: Event, handler:
  | HookHandler<Events[Event][0], Events[Event][1]>
  | HookHandlerProvider<Events[Event][0], Events[Event][1]>): boolean;

Remove hook handler for a given event.

Type Parameters

Type Parameter
Event extends string | number | symbol

Parameters

Parameter	Type	Description
event	Event	The event name to remove the handler from
handler	| HookHandler<Events[Event][0], Events[Event][1]> | HookHandlerProvider<Events[Event][0], Events[Event][1]>	The hook handler to remove

Returns

boolean

Example

const hooks = new Hooks();
const handler = function hashPassword(user) {};

hooks.add("saving", handler);

// Later, remove the handler
const removed = hooks.remove("saving", handler);
console.log(removed); // true if handler was found and removed

---

runner()

runner<Event>(action: Event): Runner<Events[Event][0], Events[Event][1]>;

Returns an instance of the runner to run hooks

Type Parameters

Type Parameter
Event extends string

Parameters

Parameter	Type	Description
action	Event	The event name to create a runner for

Returns

Runner<Events[Event][0], Events[Event][1]>

Example

const hooks = new Hooks();

hooks.add("saving", function hashPassword(user) {
  user.password = hash(user.password);
});

// Get a runner and execute hooks
const runner = hooks.runner("saving");
await runner.run(user);