Nocache Middleware

Common errors

• TypeError: nocache is not a function

  cause This error typically occurs when `nocache` is passed directly to `app.use()` without being called as a function, e.g., `app.use(nocache);`.
  fix The `nocache` export is a factory function that returns the actual middleware. You must call it, even with no arguments, before passing its result to `app.use()`: `app.use(nocache());`.

Warnings

• breaking Version 4.0.0 of `nocache` updated its minimum Node.js engine requirement to `>=16.0.0`. Older Node.js versions are not officially supported and may encounter issues.
  Fix: Upgrade your Node.js environment to version 16.0.0 or higher to ensure compatibility and access the latest features and security updates.
• gotcha Applying `nocache` globally to an Express application can have significant performance implications for your users and server. By disabling all client-side caching, every asset (HTML, CSS, JS, images) must be re-downloaded on each request, increasing network traffic and server load.
  Fix: Carefully consider where `nocache` is applied. For static assets or content that changes infrequently, consider applying `nocache` only to specific routes (e.g., `app.get('/admin', nocache(), ...)`) or using more granular cache control strategies.
• gotcha The `nocache` middleware sets specific HTTP headers (`Cache-Control`, `Expires`, `Surrogate-Control`). If other middleware, your web server (e.g., Nginx, Apache), or a reverse proxy also manipulates caching headers, there might be conflicts or unintended behavior where `nocache`'s headers are overwritten or fail to take effect as expected.
  Fix: Review the order of middleware in your application and the configuration of your web server/proxy. Ensure `nocache` is applied at a point where its headers will not be overridden by subsequent processes if you intend for it to be the authoritative cache control mechanism.

Install

• npm install nocache npm
• yarn add nocache yarn
• pnpm add nocache pnpm

Imports

• nocache
  wrong:

  const nocache = require('nocache'); // CommonJS is still supported but ESM is preferred in modern applications.

  correct:

  import nocache from 'nocache';

  The `nocache` export is a function that returns the middleware. It must be called (`nocache()`) before being passed to `app.use()`.
• nocache
  wrong:

  import nocache from 'nocache'; // While possible, for CJS-only projects, 'require' is the correct syntax.

  correct:

  const nocache = require('nocache');

  For CommonJS environments, `require` is the standard way to import. Ensure you still call it as a function: `app.use(nocache());`.

Quickstart

Demonstrates how to initialize an Express application and apply the `nocache` middleware globally, ensuring all HTTP responses include headers designed to disable client-side caching.

import express from 'express';
import nocache from 'nocache';

const app = express();
const port = process.env.PORT ?? 3000;

// Apply the nocache middleware globally to all routes.
// This ensures that all responses from this server attempt to disable client-side caching.
app.use(nocache());

app.get('/', (req, res) => {
  res.send('<h1>Welcome!</h1><p>This content should not be cached by your browser.</p>');
});

app.get('/api/data', (req, res) => {
  // Even API endpoints will have caching headers applied, forcing fresh requests.
  res.json({ message: 'Dynamic data from API', timestamp: new Date().toISOString() });
});

app.listen(port, () => {
  console.log(`Nocache server listening on port ${port}`);
  console.log('Inspect network requests in your browser to see Cache-Control, Expires, and Surrogate-Control headers set to disable caching.');
});