jointz

Zero dependency universal TypeScript validation library. Similar interface to Joi but without all the bloat, and built for browsers and node with zero dependencies.

Features

• Written in TypeScript
• Zero dependencies, tiny, and well tested
• Pretty fast
• Infer TypeScript types from validators
• Supports any, string, number, array, tuple, constant, boolean, or and object validation
• Implement your own validator and use it with any of the other validators
• Fluid immutable interface
• Targets both browsers and node

Installation

You can install it via npm

npm i --save jointz

or yarn

yarn add jointz

Usage

Import the default export from jointz

import jointz from 'jointz';

Then use it to construct validators

const ThingValidator = jointz.object({
  id: jointz.string().uuid(),
  name: jointz.string().minLength(3).maxLength(100)
}).requiredKeys(['id', 'name']);

The validator can now be used to check for errors. Validator#validate returns an array of validation errors, which is empty if the value passes validation.

const myObject = { id: 'abc', name: 'hello world!' };

const errors = ThingValidator.validate(myObject); // expect an error because id is not a uuid

if (errors.length) {
  // Fail
} else {
  // Continue
}

You can also generate TypeScript types from your validators, using Infer, or get the resulting type from validation via checkValid.

type Thing = Infer<typeof ThingValidator>;

const myObject: unknown = { id: 'abc', name: 'hello world!' };

try {
  const thing: Thing = ThingValidator.checkValid(myObject);
} catch (validationError) {
  console.log(validationError.errors);
}

jointz validators also expose the type guard function isValid on every validator.

const myObject: unknown = { id: 'abc', name: 'hello world!' };

if (ThingValidator.isValid(myObject)) {
    // This works because myObject is a valid Thing
    const id: string = myObject.id;
}

Errors

Errors match the following interface:

interface ValidationError {
  // Array of keys indicating where the validation failed. This is empty if top level validation failed.
  path: Array<string | number>;
  // The error message describing the failed validation.
  message: string;
  // The value that failed validation. This value may not be defined, e.g. in the case of missing required keys.
  value?: unknown;
}

A single validator can produce many errors. However, validators will only produce relevant errors, e.g. a number validator that checks a number is a multiple of 2 will not produce an additional error about the multiple when validating a string.