PaulBlanche/typed-validator

typed-validator

Validate (runtime) and cast (compile-time) data.

motivation

With typescript we can strongly type our code. But when we recieve a JSON from "outside", we have : * to validate it hold the expected type at runtime. * to cast it to the expected type at compile-time. This is redudant. After validating that this property is a string, it should by string typed ! Needing to both validate and cast means our code is not DRY.

This library defines composable validators that can be used to validate and cast custom types

usage

import { validate, object, string, value, array, union2 } from 'typed-validator';

const adultValidator = object({
    type: value('adult'),
    name: string(),
    job: string(),
});

const childValidator = object({
    type: value('adult'),
    name: string(),
    parents: array(string())
})

const houseValidator = object({
    address: string(),
    occupants: array(union2(childValidator, adultValidator))
})

const any:any = JSON.parse(`{
    "address": "276 Ronsom street",
    "occupants": [{
        "type": "adult",
        "name": "Mark",
        "job": "cook",
    }, {
        "type": "adult",
        "name": "Jane",
        "job": "laywer",
    }, {
        "type": "adult",
        "name": "Agatha",
        "job": "retired",
    }, {
        "type": "child",
        "name": "Timmy",
        "parents": ["Jane", "Mark"]
    }]
}`);

const house = validate(houseValidator)(any);
    /* typeof house = { 
            address:string, 
            occupants: (
                { type:'adult', name:string, job:string }|
                {type:'child', name:string, parents:string[] }
            )[] 
        }
    */

The function validate will type the result according to the types defined in the validator. validate will throw an exception if the "validatee" does not pass the validation.

validators

any()

Validate anything

<T> array(validator:Validator<T>)

Validate that the object is an array, and that each item is validated by validator.

boolean()

Validate that the object is a boolean.

nihil()

Validate that the object is null.

number()

Validate that this object is a number.

object(definition:ObjectDefinition)

Validate tha the object is an object, and that each property is validated by the corresponding property on definition.

<T> optional(validator:Validator<T>)

Validate that the object is null or undefined, or that it is validated by validator.

string()

Validate that the object is a string.

<...T> union(...validators:Validator<T>[])

Validate that the object validate at least one of the validator in validators.

<V> value(val:V)

Validate that the object is exactly the value