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Middleware

Middleware files (+middleware.js) process requests before they reach your templates. Use middleware to:

  • Check authentication
  • Load shared data
  • Set headers
  • Validate requests
  • Handle errors

Basic Example

/** @type {import('pocketpages').MiddlewareLoaderFunc} */
module.exports = function (api) {
  const { request, redirect } = api

  // Check auth
  if (!request.header('Authorization')) {
    redirect('/login')
    return {}
  }

  // Load data
  const categories = $app.findRecordsByFilter('categories', {
    filter: 'active = true',
  })

  return { categories }
}

How Middleware Works

Middleware executes hierarchically from root to leaf:

pb_hooks/pages/
  +middleware.js         # Runs first (all routes)
  products/
    +middleware.js       # Runs second (/products/*)
    [id]/
      +middleware.js     # Runs third (/products/[id]/*)

For URL /products/123:

  1. /+middleware.js runs
  2. /products/+middleware.js runs
  3. /products/[id]/+middleware.js runs

Common Use Cases

Auth Guard

/** @type {import('pocketpages').MiddlewareLoaderFunc} */
module.exports = function (api) {
  const { request, redirect } = api

  const session = request.cookie('session')
  if (!session) {
    redirect('/login')
    return {}
  }

  const user = findRecordByFilter('users', {
    filter: `session = "${session}"`,
  })

  return { user }
}

Request Validation

/** @type {import('pocketpages').MiddlewareLoaderFunc} */
module.exports = function (api) {
  const { request, response, params } = api

  if (!params.id?.match(/^[0-9]+$/)) {
    response.status(400)
    return { error: 'Invalid ID' }
  }

  return {}
}

Loading Data

/** @type {import('pocketpages').MiddlewareLoaderFunc} */
module.exports = function (api) {
  const { params, response } = api

  const product = findRecordByFilter('products', {
    filter: `id = "${params.id}"`,
  })

  if (!product) {
    response.status(404)
    return { error: 'Not found' }
  }

  return { product }
}

Controlling Middleware Execution

Middleware supports an optional second argument: next.

  • If the next argument is omitted:

    • Middleware behaves as if next() is called automatically when the function exits.
    • Execution will always continue to the next middleware or default handler.

  • If the next argument is included:

    • Any data passed to next is merged with and overwrites previous data keys.
    • Middleware will not proceed unless next() is called.
    • The page route will only be rendered if next() is called all the way through the chain.
    • If you return early (without calling next()), execution stops, no further middleware or loaders (+load, +get, etc) will run, no plugin onRender will be called, and no response will be sent. You must manually send a response, e.g. response.json(400, { error: 'Forbidden' }).

Example with next

/** @type {import('pocketpages').MiddlewareLoaderFunc} */
module.exports = function (api, next) {
  const { params, response } = api

  if (!params.id?.match(/^[0-9]+$/)) {
    return response.json(400, { error: 'Invalid ID' })
  }

  next({ validatedId: parseInt(params.id, 10) })
}

This allows fine-grained control over flow and shared data between middleware layers.

Using Middleware Data

Access middleware data in templates through data:

<% if (data.user) { %>
  <h1>Welcome, <%= data.user.name %></h1>

  <% if (data.product) { %>
    <h2><%= data.product.name %></h2>
    <p><%= data.product.description %></p>
  <% } %>
<% } %>

Important Notes

  • Middleware runs before page loaders (+load.js)
  • All middleware along the route path executes
  • Return an object to pass data to templates
  • Return early to stop processing
  • Keep processing efficient

HTTP Method-Specific Middleware

In addition to +middleware.js which runs for all HTTP methods, you can create method-specific middleware files that only run for specific HTTP methods:

// +get.js - Only runs for GET requests
/** @type {import('pocketpages').MiddlewareLoaderFunc} */
module.exports = function (api) {
  // Handle GET requests
  return {}
}

// +post.js - Only runs for POST requests
/** @type {import('pocketpages').MiddlewareLoaderFunc} */
module.exports = function (api) {
  // Handle POST requests
  return {}
}

Supported method-specific middleware files:

  • +get.js
  • +post.js
  • +put.js
  • +patch.js
  • +delete.js

These files follow the same hierarchical execution order as +middleware.js.

Reference