# Class AsyncResource

The class `AsyncResource` is designed to be extended by the embedder's async resources. Using this, users can easily trigger the lifetime events of their own resources.

The `init` hook will trigger when an `AsyncResource` is instantiated.

The following is an overview of the `AsyncResource` API.

    import { AsyncResource, executionAsyncId } from 'node:async_hooks';

    // AsyncResource() is meant to be extended. Instantiating a
    // new AsyncResource() also triggers init. If triggerAsyncId is omitted then
    // async_hook.executionAsyncId() is used.
    const asyncResource = new AsyncResource(
      type, { triggerAsyncId: executionAsyncId(), requireManualDestroy: false },
    );

    // Run a function in the execution context of the resource. This will
    // * establish the context of the resource
    // * trigger the AsyncHooks before callbacks
    // * call the provided function `fn` with the supplied arguments
    // * trigger the AsyncHooks after callbacks
    // * restore the original execution context
    asyncResource.runInAsyncScope(fn, thisArg, ...args);

    // Call AsyncHooks destroy callbacks.
    asyncResource.emitDestroy();

    // Return the unique ID assigned to the AsyncResource instance.
    asyncResource.asyncId();

    // Return the trigger ID for the AsyncResource instance.
    asyncResource.triggerAsyncId();

#### Hierarchy

- AsyncResource
  - EventEmitterReferencingAsyncResource

#####
Index

### Constructors

constructor

### Methods

asyncId
bind
emitDestroy
runInAsyncScope
triggerAsyncId
bind

## Constructors

### constructor

- new AsyncResource(type, triggerAsyncId?): AsyncResource

- AsyncResource() is meant to be extended. Instantiating a new AsyncResource() also triggers init. If triggerAsyncId is omitted then async_hook.executionAsyncId() is used.

  #### Parameters

  - ##### type: string

    The type of async event.

  - ##### `Optional` triggerAsyncId: number | AsyncResourceOptions

    The ID of the execution context that created this async event (default: `executionAsyncId()`), or an AsyncResourceOptions object (since v9.3.0)

  #### Returns AsyncResource

## Methods

### asyncId

- asyncId(): number

- #### Returns number

  The unique `asyncId` assigned to the resource.

### bind

- bind<Func>(fn): Func

- Binds the given function to execute to this `AsyncResource`'s scope.

  #### Type Parameters

  - #### Func extends ((...args) => any)

  #### Parameters

  - ##### fn: Func

    The function to bind to the current `AsyncResource`.

  #### Returns Func

  #### Since

  v14.8.0, v12.19.0

### emitDestroy

- emitDestroy(): AsyncResource

- Call all `destroy` hooks. This should only ever be called once. An error will be thrown if it is called more than once. This must be manually called. If the resource is left to be collected by the GC then the `destroy` hooks will never be called.

  #### Returns AsyncResource

  A reference to `asyncResource`.

### runInAsyncScope

- runInAsyncScope<This, Result>(fn, thisArg?, ...args): Result

- Call the provided function with the provided arguments in the execution context of the async resource. This will establish the context, trigger the AsyncHooks before callbacks, call the function, trigger the AsyncHooks after callbacks, and then restore the original execution context.

  #### Type Parameters

  - #### This

  - #### Result

  #### Parameters

  - ##### fn: ((this, ...args) => Result)

    The function to call in the execution context of this async resource.

    - - (this, ...args): Result

      - #### Parameters

        - ##### this: This

        - ##### `Rest` ...args: any[]

        #### Returns Result

  - ##### `Optional` thisArg: This

    The receiver to be used for the function call.

  - ##### `Rest` ...args: any[]

    Optional arguments to pass to the function.

  #### Returns Result

  #### Since

  v9.6.0

### triggerAsyncId

- triggerAsyncId(): number

- #### Returns number

  The same `triggerAsyncId` that is passed to the `AsyncResource` constructor.

### `Static` bind

- bind<Func, ThisArg>(fn, type?, thisArg?): Func

- Binds the given function to the current execution context.

  #### Type Parameters

  - #### Func extends ((this, ...args) => any)

  - #### ThisArg

  #### Parameters

  - ##### fn: Func

    The function to bind to the current execution context.

  - ##### `Optional` type: string

    An optional name to associate with the underlying `AsyncResource`.

  - ##### `Optional` thisArg: ThisArg

  #### Returns Func

  #### Since

  v14.8.0, v12.19.0

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