Express Context

A lightweight and type-safe HTTP context helper for Express, built using Node.js’s native AsyncLocalStorage. It allows you to safely store and access per-request data (like user info, trace IDs, etc.) across your entire app — including in async functions and services.

Installation

$ npm install --save @k_ankit/express-context

Why Use This?

Keep track of per-request data without passing it manually Built on top of AsyncLocalStorage (no external dependencies) Type-safe and easy to use Framework-agnostic, but designed for Express

Usage

1. Import the helpers

import { contextMiddleware, getContext, setContext } from '@k_ankit/express-context';
import express from 'express';

2. Register the middleware Place the contextMiddleware early in your Express app or specific routes:

const app = express();
app.use(contextMiddleware); // Global registration

Or apply it per route:

const TestRouter = express.Router();

TestRouter.get('/test', contextMiddleware, (req, res) => {
  setContext('key', { value: 'test' });

  const data = getContext<{ value: string }>('key');
  console.log(data); // { value: 'test' }

  res.send('Context stored!');
});

API

contextMiddleware(req, res, next) : Initializes async context for each request. Required before using setContext or getContext.

setContext(key: string, value: any) : Stores a value in the current request’s context.

getContext<T = any>(key: string): T | undefined : Retrieves the value for a given key from the current request’s context.