Hooks

Hooks provide a simple way to execute logic before and/or after the handler runs for a route in Galbe.

Defining Hooks

const hook = async (context, next) => {
  context.state['foo'] = 'bar'
  await next()
  console.log('Hook end')
}

A hook takes two arguments: context and next.

context

The context object contains request information and a modifiable state property that persists across all hooks and the handler. This is useful for sharing data between hooks and the handler. See the Context section for full details.

next

The next function calls the next hook in the chain, or the handler if the current hook is the last one. It should be called at most once. If a hook does not call next (and does not return a response), Galbe will call it automatically when the hook returns.

Tip

Hooks are preemptable: they can return a response at any time to short-circuit the chain. This is useful for authentication, authorization, caching, and similar concerns.

For more details on response handling, see Response Types.

Declaring Hooks

Hooks are declared before the handler in the Route Definition, as an array of hook functions.

galbe.get('/foo', [hook1, hook2, ...], ctx => {})

Hooks execute in the order they are declared, just before the Handler. For more on where hooks fit in the request lifecycle, see the Lifecycle section.

Examples

Linear Hook Execution

const hook1 = context => {
  console.log('hook1 called')
}
const hook2 = context => {
  console.log('hook2 called')
}

galbe.get('/example', [hook1, hook2], ctx => {
  console.log('handler')
})

$ curl http://localhost:3000/example

hook1 called

hook2 called

handler

Nested Hook Execution

const hook1 = async (context, next) => {
  console.log('hook1 start')
  await next()
  console.log('hook1 end')
}
const hook2 = async (context, next) => {
  console.log('hook2 start')
  await next()
  console.log('hook2 end')
}

galbe.get('/example', [hook1, hook2], ctx => {
  console.log('handler')
})

$ curl http://localhost:3000/example

hook1 start

hook2 start

handler

hook2 end

hook1 end