type.md

Types

The types module can be used directly to validate records, function arguments, lists, single values, etc.

You can import it as

import T, { validateRecord } from 'enum-fp/types';

The Type module exposes the following -

• T
• isOfType
• validateRecord

Type sum-type

data T = Any | String | Number | Bool | Record (Object T) | Map T | List T? | Enum EnumType | OneOf [T];

You can check if a value is of a particular type by using the isOfType function (Refer to section below for more info about isOfType)

const isString = isOfType(T.String());

isString('Hello world') // > true
isString(1) // > false

isOfType

isOfType :: T -> a -> Boolean

You can use this function to write helper functions for validating types

const isString = isOfType(T.String());
const isNumber = isOfType(T.Number());

const isUser = isOfType(T.Record({
    name: T.String(),
    age: T.Number(),
}));

isUser({ name: 'Akshay Nair', age: 21 }); // > true
isUser({ name: 'Akshay Nair', age: '21' }); // > false
isUser({ name: 'Akshay Nair' }); // > false

validateRecord

validateRecord :: (Object T, a) -> Boolean

Validates if the passed object is of the specified shape. The check is strict so missing fields in an object means the object is invalid. (Kind of an alternate api for isOfType(T.Record({ /* shape */ })))

Here's the above isOfType example for user

const isUser = user => validateRecord({
    name: T.String(),
    age: T.Number(),
}, user);

#### Next topic