typecheck's Introduction

typecheck

Simple, strict, extensible runtime type checker for JavaScript.

Basic usage

import T from '@umbrellio/typecheck'

// define a type
const userType = T.Struct({
  email: T.String,
  password: T.String,
  age: T.Option(T.Number),
  role: T.Sum('admin', 'support'),
})

// run a type check
T.check(userType, {
  email: '[email protected]',
  password: '12345',
  age: 12,
  role: 'admin',
}) // => true

Installation

Install with yarn:

$ yarn add @umbrellio/typecheck
# or with npm:
$ npm i -S @umbrellio/typecheck

Built-in type reference

Primitive types

T.String: kek, new String('pek')
T.Number: 69, new Number(100), -2131.31
T.Boolean: true, false

Arrays

Signature: T.Array(type)

T.Array(T.String) // [], ['kek', 'pek']
T.Array(T.Sum(T.Boolean, T.Number)) // [], [true, 1]

Option

Signature: T.Option(type)

T.Option(T.String) // null, undefined, 'some string'
T.Option(T.Array(T.Number)) // null, undefined, [], [69]

Struct

Signature: T.Struct(schema) where schema is an object

T.Struct({ name: T.String }) // { name: 'Ivan' }
T.Struct({ email: T.String, age: T.Option(T.Number) }) // { email: '[email protected]', age: 69 }

Sum

Signature: T.Sum(...types)

T.Sum(T.Number, T.String, T.Struct({ name: T.String })) // 69, '69', { name: 'ivan' }

Advanced usage

Custom types

import T from '@umbrellio/typecheck'

// age is a positive number
const Age = new T.Type(v => T.check(T.Number, v) && v > 0)

const userType = T.Struct({
  email: T.String,
  age: T.Option(Age),
})