| # Asynchronous operations |
| |
| Node.js native add-ons often need to execute long running tasks and to avoid |
| blocking the **event loop** they have to run them asynchronously from the |
| **event loop**. |
| In the Node.js model of execution the event loop thread represents the thread |
| where JavaScript code is executing. The Node.js guidance is to avoid blocking |
| other work queued on the event loop thread. Therefore, we need to do this work on |
| another thread. |
| |
| All this means that native add-ons need to leverage async helpers from libuv as |
| part of their implementation. This allows them to schedule work to be executed |
| asynchronously so that their methods can return in advance of the work being |
| completed. |
| |
| Node Addon API provides an interface to support functions that cover |
| the most common asynchronous use cases. There is an abstract classes to implement |
| asynchronous operations: |
| |
| - **[`Napi::AsyncWorker`](async_worker.md)** |
| |
| This class helps manage asynchronous operations through an abstraction |
| of the concept of moving data between the **event loop** and **worker threads**. |
| |
| Also, the above class may not be appropriate for every scenario. When using any |
| other asynchronous mechanism, the following API is necessary to ensure an |
| asynchronous operation is properly tracked by the runtime: |
| |
| - **[AsyncContext](async_context.md)** |
| |
| - **[CallbackScope](callback_scope.md)** |
