chkr

js type check

Installation

npm install chkr

Example

const {Num, Optional, Arr, Str, Bool} = require('chkr');

//simple type check
Num(1) //==> 1
Num('1') //throws error
Num('a') //throws error

//type combination
Optional(Num)(undefined) //===> undefined
Arr(Num)([1,2,3]) //===> [1,2,3]

console.log(Obj({
  user: Str,
  age: Num,
  isAdmin: Bool,
  pages: Arr(Str)
}).sample())

API

Type

a type is a js function with sample as it's method. it's inspect symbol is customized to show the infomation of itself.

Type()

type function checks and parse the input value and returns then transformed value or throw an error if the input value is not the required type

.sample

sample method returns a sample data of a type

Concrete Type

• Id any type
• Null null or undefined
• Any any thing but not Null
• Num input a number or a string consist of only digits will output a exact number
• Str any thing will transfer to string
• Bool true or 'true' to true, false or 'false' to false, number, object... throws
• Time Date or any thing can be transfered into Date by new Date

Type Combinator

• Const a type with only one value (1)
• Or accept some types returns a type which can be all the given types (+)
• Obj accept an object indicate an object has some key with some type (*)
• Optional make type optional (Null + Type)
• Kv accept a type called value type to generate a key value paire object type
• Arr Array of a type

Recursive Type Def

recursive type is supported using a fn withSelf. you can use this to define an List

const List = ValueType => withSelf(Self => Or(Const(Empty), Obj({head: ValueType, tail: Self})))
const NumList = List(Num)

Test

$ npm test
$ npm run test-cov