fefe

fefe

Validate, sanitize and transform values with proper types.

🔎 Validation: checks a value (example: check if value is string)
⚙ Sanitization: if a value is not valid, try to transform it (example: transform value to Date)
🛠️ Transformation: transforms a value (example: parse JSON)
🔌 Schemas are functions: easily extendable

🔎 Validation example

Validation only checks the provided value and returns it with proper types.

import { validate } from 'fefe'

const validatePerson = validate.object({ name: validate.string() })

// result is of type { name: string }
const person = validatePerson({ name: 'Leia' })

// throws FefeError because 'foo' is not a valid property
validatePerson({ foo: 'bar' })

You can also use fefe to define your types easily:

type Person = ReturnType<typeof validatePerson> // { name: string }

⚙️ Sanitization example

import { sanitize, validate } from 'fefe'

const sanitizeMovie = validate.object({
  title: validate.string(),
  releasedAt: sanitize.date()
})

// { title: string, releasedAt: Date }
type Movie = ReturnType<typeof sanitizeMovie>

const book: Book = sanitizeMovie({
  title: 'Star Wars',
  releasedAt: '1977-05-25T12:00:00.000Z'
})

Then book equals { title: 'Star Wars', releasedAt: Date(1977-05-25T12:00:00.000Z) } (releasedAt now is a date).

🛠️ Transformation example

This is an example that can be applied to parsing environment variables or query string parameters. Note how easy it is to apply a chain of functions to transform and validate a value (here we use ramda).

import { transform, validate } from 'fefe'
import { pipe } from 'ramda'

const parseConfig = validate.object({
  gcloudCredentials: pipe(
    validate.string(),
    transform.parseJson(),
    validate.object({ key: validate.string() })
  ),
  whitelist: pipe(validate.string(), str => str.split(','))
})

// { gcloudCredentials: { key: string }, whitelist: string[] }
type Config = ReturnType<typeof parseConfig>

const config: Config = parseConfig({
  gcloudCredentials: '{"key":"secret"}',
  whitelist: 'alice,bob'
})

Then config will equal { gcloudCredentials: { key: 'secret'}, whitelist: ['alice', 'bob'] }.

Note: you can use validations in transformations.