@wry/context

What is @wry/context?

The @wry/context npm package provides a mechanism for managing contextual information across asynchronous operations without relying on global state or directly passing context through function calls. It's particularly useful for tracking execution contexts across async boundaries, making it easier to implement features like request-scoped logging, performance monitoring, and more in a way that's transparent to the code that's being executed.

What are @wry/context's main functionalities?

Creating and using a context

This feature demonstrates how to create a new context and use it to store and retrieve values within a specific execution scope. The `withValue` method temporarily sets a value for a given key in the context, which can be accessed using the `get` method within the callback passed to `withValue`. Outside of this callback, the context does not hold the value, showcasing how @wry/context can manage context-specific data without leaking it outside of the intended scope.

const {Slot} = require('@wry/context');
let context = new Slot();
context.withValue('myKey', 'myValue', () => {
  // Within this function, context.get('myKey') will return 'myValue'.
  console.log(context.get('myKey')); // Outputs: 'myValue'
});
// Outside, context.get('myKey') returns undefined.
console.log(context.get('myKey')); // Outputs: undefined

Other packages similar to @wry/context

cls-hooked

The cls-hooked package provides a similar functionality to @wry/context by allowing the creation of context namespaces that can be used to store and access data across asynchronous calls. It uses the async_hooks module in Node.js to achieve this. Compared to @wry/context, cls-hooked is more tightly integrated with Node.js's async model but might be more complex to use due to its reliance on async_hooks.

continuation-local-storage

This package also offers context management capabilities similar to @wry/context, enabling the association of state with chains of asynchronous calls. It's an earlier solution compared to cls-hooked and might not be as efficient or reliable in certain Node.js versions or scenarios. Compared to @wry/context, continuation-local-storage provides a broader API but may suffer from the limitations of its underlying implementation.

README

@wry/context

Manage contextual information needed by synchronous or asynchronous tasks without explicitly passing objects around.