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📄 useEventBus

📊 Analysis Summary

Metric	Count
🔧 Functions	8
📦 Imports	3
📐 Interfaces	2
📑 Type Aliases	3

📚 Table of Contents

• Imports
• Functions
• Interfaces
• Type Aliases

🛠️ File Location:

📂 packages/core/useEventBus/index.ts

📦 Imports

Name	Source
Fn	@vueuse/shared
tryOnScopeDispose	@vueuse/shared
events	./internal

---

Functions

useEventBus(key: EventBusIdentifier<T>): UseEventBusReturn<T, P>

Parameters:

• key EventBusIdentifier<T>

Returns: UseEventBusReturn<T, P>

Calls:

• events.get
• listeners.add
• events.set
• off
• tryOnScopeDispose (from @vueuse/shared)
• listener
• on
• listeners.delete
• reset
• events.delete
• events.get(key)?.forEach
• v

Internal Comments:

// auto unsubscribe when scope get disposed (x3)
// @ts-expect-error cast (x3)

Code

export function useEventBus<T = unknown, P = any>(key: EventBusIdentifier<T>): UseEventBusReturn<T, P> {
  function on(listener: EventBusListener<T, P>) {
    const listeners = (events.get(key) || new Set())
    listeners.add(listener)
    events.set(key, listeners)

    const _off = () => off(listener)
    // auto unsubscribe when scope get disposed
    tryOnScopeDispose(_off)
    return _off
  }

  function once(listener: EventBusListener<T, P>) {
    function _listener(...args: any[]) {
      off(_listener)
      // @ts-expect-error cast
      listener(...args)
    }
    return on(_listener)
  }

  function off(listener: EventBusListener<T>): void {
    const listeners = events.get(key)
    if (!listeners)
      return

    listeners.delete(listener)

    if (!listeners.size)
      reset()
  }

  function reset() {
    events.delete(key)
  }

  function emit(event?: T, payload?: P) {
    events.get(key)?.forEach(v => v(event, payload))
  }

  return { on, once, off, emit, reset }
}

Internal helpers

Declared inside another function in this file.

on(listener: EventBusListener<T, P>): () => void

Parameters:

• listener EventBusListener<T, P>

Returns: () => void

Calls:

• events.get
• listeners.add
• events.set
• off
• tryOnScopeDispose (from @vueuse/shared)

Internal Comments:

// auto unsubscribe when scope get disposed (x3)

Code

function on(listener: EventBusListener<T, P>) {
    const listeners = (events.get(key) || new Set())
    listeners.add(listener)
    events.set(key, listeners)

    const _off = () => off(listener)
    // auto unsubscribe when scope get disposed
    tryOnScopeDispose(_off)
    return _off
  }

_off(): void

Returns: void

Calls:

• off

Code

() => off(listener)

once(listener: EventBusListener<T, P>): () => void

Parameters:

• listener EventBusListener<T, P>

Returns: () => void

Calls:

• off
• listener
• on

Internal Comments:

// @ts-expect-error cast (x3)

Code

function once(listener: EventBusListener<T, P>) {
    function _listener(...args: any[]) {
      off(_listener)
      // @ts-expect-error cast
      listener(...args)
    }
    return on(_listener)
  }

_listener(args: any[]): void

Parameters:

• args any[]

Returns: void

Calls:

• off
• listener

Internal Comments:

// @ts-expect-error cast (x3)

Code

function _listener(...args: any[]) {
      off(_listener)
      // @ts-expect-error cast
      listener(...args)
    }

off(listener: EventBusListener<T>): void

Parameters:

• listener EventBusListener<T>

Returns: void

Calls:

• events.get
• listeners.delete
• reset

Code

function off(listener: EventBusListener<T>): void {
    const listeners = events.get(key)
    if (!listeners)
      return

    listeners.delete(listener)

    if (!listeners.size)
      reset()
  }

reset(): void

Returns: void

Calls:

• events.delete

Code

function reset() {
    events.delete(key)
  }

emit(event: T, payload: P): void

Parameters:

• event T
• payload P

Returns: void

Calls:

• events.get(key)?.forEach
• v

Code

function emit(event?: T, payload?: P) {
    events.get(key)?.forEach(v => v(event, payload))
  }

---

Interfaces

EventBusKey<T>

Interface Code

export interface EventBusKey<T> extends Symbol { }

UseEventBusReturn<T, P>

Interface Code

export interface UseEventBusReturn<T, P> {
  /**
   * Subscribe to an event. When calling emit, the listeners will execute.
   * @param listener watch listener.
   * @returns a stop function to remove the current callback.
   */
  on: (listener: EventBusListener<T, P>) => Fn
  /**
   * Similar to `on`, but only fires once
   * @param listener watch listener.
   * @returns a stop function to remove the current callback.
   */
  once: (listener: EventBusListener<T, P>) => Fn
  /**
   * Emit an event, the corresponding event listeners will execute.
   * @param event data sent.
   */
  emit: (event?: T, payload?: P) => void
  /**
   * Remove the corresponding listener.
   * @param listener watch listener.
   */
  off: (listener: EventBusListener<T>) => void
  /**
   * Clear all events
   */
  reset: () => void
}

Properties

Name	Type	Optional	Description
on	(listener: EventBusListener<T, P>) => Fn	✗	not shown
once	(listener: EventBusListener<T, P>) => Fn	✗	not shown
emit	(event?: T, payload?: P) => void	✗	not shown
off	(listener: EventBusListener<T>) => void	✗	not shown
reset	() => void	✗	not shown

---

Type Aliases

EventBusListener<T = unknown, P = any>

type EventBusListener<T = unknown, P = any> = (event: T, payload?: P) => void;

EventBusEvents<T, P = any>

type EventBusEvents<T, P = any> = Set<EventBusListener<T, P>>;

EventBusIdentifier<T = unknown>

type EventBusIdentifier<T = unknown> = EventBusKey<T> | string | number;

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