👋 Introduction to Middleware

A middleware is a function that takes a context, and a function that will apply the next middleware. It is a good idea to use the async keyword for these functions so you can use await.

Sunder ships with some middleware, it is up to you to compose them. For any non-trivial app you should use the Router middleware.

Example one: Middleware that logs all requests#

// Note that in Cloudflare Workers this will always log 0ms as Date.now() always
// returns the time of the request instead of the wall clock time.
async function logRequestsMiddleware(ctx, next: Middleware) {
  const start = Date.now();
  await next();
  const ms = Date.now() - start;
  console.log(`${ctx.method} ${ctx.url} - ${ms}ms`);
}

Example two: Middleware that prints all errors to console#

async function logErrorsMiddleware(ctx, next: Middleware) {
  try {
    await next();
  } catch(e) {
    console.error(e);
    throw e;
  }
}

Example one: Middleware that logs all requests#

Example two: Middleware that prints all errors to console#

Further reading#