fox-validator

A value validation library with a jest like api.

We want to ensure that every IO function of our code base ensures the incoming or outgoing data is a valid fox. TypeScript doesn't provide a way to do this.

With fox-validator we can validate incoming data. It produces a custom type guard function.

Usage

import { FunctionValidator, ObjectValidator } from "../src/index"

/* Our target data type */
interface Fox {
    say(): string
}

/* Validator function definition */
const isFox = new ObjectValidator<Fox>().map({
    say: new FunctionValidator().expectsArgumentCount(0).seal(),
}).seal()

/* Defining test data */
const fox: unknown = {
    say: () => "🦊"
}
// fox is of type `unknown`

if (isFox(fox)) {
    // fox is of type `Fox`
    // lets see what the fox say...
    console.log(fox.say()) // > 🦊
}
// fox is of type `unknown`

API

The library provides several validator generators. These generators are available:

• AnyValidator: Returns true for every given value.
• ArrayValidator: Validates array objects and their contained elements.
• BooleanValidator: Checks a given value for be type of boolean and provides methods to ensure the value of the boolean (true or false).
• FunctionValidator: Ensures the given value is a function. It also provides a method to validate the argument length of the given function.
• MaybeValidator: Proxies another validator. A given value has to be undefined or needs to be validated by another given validator.
• NullValidator: Returns true if the value is equal to null.
• NumberValidator: Ensures a given value is a number. This generator also provides methods to check the number.
• ObjectValidator: A validator generator to check objects and their properties.
• OneOfValidator: A validator generator that accepts multiple validator. If one subvalidator returns true the value will be validated.
• StringValidator: This generator ensures a given value is a string. The generator also provides methods to check the string.
• UndefinedValidator: This validator returns true if the given value is undefined