types.js

// ------lib------
const getType = (o) => {
  return Object.prototype.toString.call(o).slice(8,-1).toLocaleLowerCase()
}

const types = () => {
  const func = (val) => getType(val) === 'function'
  const number = (val) => getType(val) === 'number'
  const string = (val) => getType(val) === 'string'
  const bool = (val) => getType(val) === 'boolean'
  const arrayOf = (type) => (val) => getType(val) === 'array' && type(val[0])
  const objectOf = (obj) => (val) => Object.entries(obj).every(([key, value]) => value(val[key]))
  const oneOfType = (types) => (val) => types.some(type => type(val))
  const oneOf = (values) => (val) => values.some(type => type === val)
  const sumOf = (values) => (param) => values.every((type, i) => type === param[i])

  return {
    func,
    number,
    string,
    bool,
    arrayOf,
    objectOf,
    oneOfType,
  }
}

const createType = (type) => {
  if (type) {
    return (val) => type(val) ? val : null
  }
  const newType = (otherType) => otherType === newType || newType
  return newType
}
/*
// ------feature------
const createFunc = (...types) => (fn) => (...param) => {
  const isValid = types.every((type, i) => type(param[i]))
  if (isValid === false) {
    console.error('type is not valid')
    return
  }
  fn(...param)
}

const createFuncR = (...types) => (...param) => (fn) => createFuncType(...types)(fn)(...param)
*/

// ------used------

// primitive types
const t = types()

const Person = createType(t.objectOf({
  id: t.number,
  name: t.string,
}))

const Personal = createType(t.arrayOf(Person))

const person1 = {id: 2, name: 'Alex'}
const person2 = {id: 1, name: 'Joh'}

const personal = [person1, person2]

Person(person1)

Personal(personal)

// new types

const True = createType()
const False = createType()
const Bool = t.oneOfType([True, False])