feathersHooks
Generating a hook
A new hook can be generated via
npx feathers generate hook
npx feathers generate hook
Hook name
The hook generator will first ask for a name. Based on the name it will create a kebab-cased filename in the hooks/ folder that exports a camelCased hook function. For example a name of my fancy Hook will create a src/my-fancy-hook.ts file that exports a myFancyHook hook function.
Hook types
There are two hook types that can be generated.
tip
For more information see the hooks API documentation.
Around hooks
Around hooks allow to control the entire before, after and error flow in a single function. An around hook is an async function that accepts two arguments:
- The hook context
- An asynchronous
nextfunction. Somewhere in the body of the hook function, there is a call toawait next(), which calls thenexthooks OR the original function if all other hooks have run.
ts
import type { HookContext, NextFunction } from '../declarations'
export const myFancyHook = async (context: HookContext, next: NextFunction) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
await next()
// Do things after here
}
import type { HookContext, NextFunction } from '../declarations'
export const myFancyHook = async (context: HookContext, next: NextFunction) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
await next()
// Do things after here
}
export const myFancyHook = async (context, next) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
await next()
// Do things after here
}
export const myFancyHook = async (context, next) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
await next()
// Do things after here
}
You can wrap the await next() in a try/catch block to also handle errors.
Before, after, error
Before, after or error hooks are async functions that take the hook context as the parameter.
ts
import type { HookContext } from '../declarations'
export const myFancyHook = async (context: HookContext) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
import type { HookContext } from '../declarations'
export const myFancyHook = async (context: HookContext) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
export const myFancyHook = async (context) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
export const myFancyHook = async (context) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
Context types
If the hook is for a specific service, you can pass the service as a generic to the HookContext type which will give you the correct types for context.data, context.result and context.params:
ts
import type { UserService } from '../services/users/users'
import type { HookContext } from '../declarations'
export const myFancyUserHook = async (context: HookContext<UserService>) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
import type { UserService } from '../services/users/users'
import type { HookContext } from '../declarations'
export const myFancyUserHook = async (context: HookContext<UserService>) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
export const myFancyUserHook = async (context) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
export const myFancyUserHook = async (context) => {
console.log(`Running hook ${name} on ${context.path}.${context.method}`)
}
Registering hooks
A generated hook can be registered as an application hook or as a service hook. Also see the hook registration API documentation.
Profiling example
To log some basic profiling information like which method was called and how long it took to run you can create a new around hook called profiler via
npx feathers generate hook
npx feathers generate hook
Then update src/hooks/profiler.ts as follows:
ts
import type { HookContext, NextFunction } from '../declarations'
import { logger } from '../logger'
export const profiler = async (context: HookContext, next: NextFunction) => {
const startTime = Date.now()
await next()
const runtime = Date.now() - startTime
console.log(`Calling ${context.method} on service ${context.path} took ${runtime}ms`)
}
import type { HookContext, NextFunction } from '../declarations'
import { logger } from '../logger'
export const profiler = async (context: HookContext, next: NextFunction) => {
const startTime = Date.now()
await next()
const runtime = Date.now() - startTime
console.log(`Calling ${context.method} on service ${context.path} took ${runtime}ms`)
}
import { logger } from '../logger.js'
export const profiler = async (context, next) => {
const startTime = Date.now()
await next()
const runtime = Date.now() - startTime
console.log(`Calling ${context.method} on service ${context.path} took ${runtime}ms`)
}
import { logger } from '../logger.js'
export const profiler = async (context, next) => {
const startTime = Date.now()
await next()
const runtime = Date.now() - startTime
console.log(`Calling ${context.method} on service ${context.path} took ${runtime}ms`)
}
And add it in src/app.ts as an application hook after the logError hook as follows:
ts
import { profiler } from './hooks/profiler'
//...
// Register hooks that run on all service methods
app.hooks({
around: {
all: [logError, profiler]
},
before: {},
after: {},
error: {}
})
import { profiler } from './hooks/profiler'
//...
// Register hooks that run on all service methods
app.hooks({
around: {
all: [logError, profiler]
},
before: {},
after: {},
error: {}
})
import { profiler } from './hooks/profiler.js'
//...
// Register hooks that run on all service methods
app.hooks({
around: {
all: [logError, profiler]
},
before: {},
after: {},
error: {}
})
import { profiler } from './hooks/profiler.js'
//...
// Register hooks that run on all service methods
app.hooks({
around: {
all: [logError, profiler]
},
before: {},
after: {},
error: {}
})