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Parameter Injection

Vegaa's automatic parameter injection is one of its most powerful features. It eliminates boilerplate by automatically providing values based on parameter names.

How It Works​

Vegaa analyzes your handler function's parameter names and automatically injects matching values from:

  1. Route parameters (:id, :userId, etc.)
  2. Query string parameters
  3. Request body (for POST, PUT, PATCH)
  4. Middleware-provided values

Route Parameters​

Route parameters are automatically available:

// Single parameter
route('/users/:id').get((id) => {
  return { userId: id }
})

// Multiple parameters
route('/users/:userId/posts/:postId').get((userId, postId) => {
  return { userId, postId }
})

Request Body​

For POST, PUT, and PATCH requests, the body is available:

route('/users').post((body) => {
  return { created: true, user: body }
})

Smart Grouping​

When you have both route parameters and a body, Vegaa groups them:

route('/users/:id').put((params, body) => {
  return {
    userId: params.id,    // Route parameter
    updatedData: body     // Request body
  }
})

Query Parameters​

Query string parameters are available via the query parameter:

route('/search').get((query) => {
  return {
    term: query.q,
    page: query.page || 1
  }
})

Middleware Values​

Values provided by middleware are automatically available:

vegaa.middleware(() => {
  return { user: { id: 1, name: 'John' } }
})

route('/profile').get((user) => {
  return { user }  // user is automatically injected
})

Parameter Name Matching​

Vegaa matches parameters by name:

  • id → Route parameter :id or query ?id=...
  • body → Request body
  • query → Query string object
  • params → Route parameters object
  • Any middleware-provided value name

Examples​

// Simple GET with route parameter
route('/users/:id').get((id) => ({ userId: id }))

// POST with body
route('/users').post((body) => ({ created: body }))

// PUT with both params and body
route('/users/:id').put((params, body) => ({
  userId: params.id,
  data: body
}))

// With middleware
vegaa.middleware(() => ({ timestamp: Date.now() }))
route('/time').get((timestamp) => ({ time: timestamp }))

Next Steps​