Expo Server

An error response representation which can be thrown anywhere in server-side code.

A StatusError can be thrown by a request handler and will be caught by the expo-server runtime and replaced by a Response with the status and body that's been passed to the StatusError.

import { StatusError } from 'expo-server';

export function GET(request, { postId }) {
  if (!postId) {
    throw new StatusError(400, 'postId parameter is required');
  }
}

Creates a loader function for routes that need access to the incoming HTTP request. Server loaders run on every request during SSR. If called during SSG where no request is available, this throws an error.

See: Data loaders for more information.

import { createServerLoader } from 'expo-server';

export const loader = createServerLoader(async (request, params) => {
  const authHeader = request.headers.get('Authorization');
  return { authenticated: !!authHeader };
});

Creates a loader function for routes that only need route parameters to load data. The callback receives no request object, making it safe to use for both SSG and SSR.

See: Data loaders for more information.

import { createStaticLoader } from 'expo-server';

export const loader = createStaticLoader(async (params) => {
  const post = await fetchPost(params.id);
  return { post };
});

Defers a task until after a response has been sent.

This only calls the task function once the request handler has finished resolving a Response and keeps the request handler alive until the task is completed. This is useful to run non-critical tasks after the request handler, for example to log analytics datapoints. If the request handler rejects with an error, deferred tasks won't be executed.

Returns the request's environment, if the server runtime supports this.

In EAS Hosting, the returned environment name is the alias or deployment identifier, but the value may differ for other providers.

Returns the current request's URL.

This typically returns the request's URL, or on certain platforms, the origin of the request. This does not use the Origin header in development as it may contain an untrusted value.

Returns an immutable copy of the current request's headers.

Runs a task immediately and instructs the runtime to complete the task.

A request handler may be terminated as soon as the client has finished the full Response and unhandled promise rejections may not be logged properly. To run tasks concurrently to a request handler and keep the request alive until the task is completed, pass a task function to runTask instead. The request handler will be kept alive until the task completes.

Sets headers on the Response the current request handler will return.

This only updates the headers once the request handler has finished and resolved a Response. It will either receive a set of Headers or an equivalent object containing headers, which will be merged into the response's headers once it's returned.

An immutable version of the Fetch API's Headers object. It cannot be mutated or modified.

An immutable version of the Fetch API's Request object. It cannot be mutated or modified, its headers are immutable, and you won't have access to the request body.

Middleware matcher settings that restricts the middleware to run conditionally.

Exported from a +middleware.ts file to configure the server-side middleware function.

See: https://docs.expo.dev/router/web/middleware/

import type { MiddlewareSettings } from 'expo-server';

export const unstable_settings: MiddlewareSettings = {
  matcher: {
    methods: ['GET'],
    patterns: ['/api', '/admin/[...path]'],
  },
};