runtypes

What is runtypes?

Runtypes is a TypeScript library that provides runtime validation and type checking for JavaScript objects. It allows developers to define types and validate data against those types at runtime, ensuring that the data conforms to the expected structure and types.

What are runtypes's main functionalities?

Basic Type Validation

Runtypes allows you to define basic types like String and Number and validate data against these types. If the data does not match the expected type, an error is thrown.

const { String, Number } = require('runtypes');

const Name = String;
const Age = Number;

Name.check('John Doe'); // Passes
Age.check(30); // Passes

// Name.check(123); // Throws an error
// Age.check('30'); // Throws an error

Object Validation

Runtypes allows you to define complex types like objects and validate data against these types. You can specify the structure of the object and the types of its properties.

const { Record, String, Number } = require('runtypes');

const Person = Record({
  name: String,
  age: Number
});

Person.check({ name: 'John Doe', age: 30 }); // Passes

// Person.check({ name: 'John Doe', age: '30' }); // Throws an error

Union Types

Runtypes supports union types, allowing you to define a type that can be one of several types. This is useful for validating data that can have multiple valid types.

const { Union, String, Number } = require('runtypes');

const StringOrNumber = Union(String, Number);

StringOrNumber.check('Hello'); // Passes
StringOrNumber.check(123); // Passes

// StringOrNumber.check(true); // Throws an error

Array Validation

Runtypes allows you to define array types and validate data against these types. You can specify the type of the elements in the array.

const { Array, String } = require('runtypes');

const StringArray = Array(String);

StringArray.check(['Hello', 'World']); // Passes

// StringArray.check(['Hello', 123]); // Throws an error

Optional Properties

Runtypes allows you to define optional properties in objects. This is useful for validating data where some properties may or may not be present.

const { Record, String, Number, Optional } = require('runtypes');

const Person = Record({
  name: String,
  age: Optional(Number)
});

Person.check({ name: 'John Doe' }); // Passes
Person.check({ name: 'John Doe', age: 30 }); // Passes

// Person.check({ name: 'John Doe', age: '30' }); // Throws an error

Other packages similar to runtypes

io-ts

io-ts is a runtime type system for IO decoding/encoding in TypeScript. It provides similar functionality to runtypes, allowing you to define types and validate data at runtime. However, io-ts has a more functional programming approach and integrates well with fp-ts.

zod

Zod is a TypeScript-first schema declaration and validation library. It provides a similar feature set to runtypes, allowing you to define schemas and validate data at runtime. Zod is known for its simplicity and ease of use.

yup

Yup is a JavaScript schema builder for value parsing and validation. It is similar to runtypes in that it allows you to define schemas and validate data. Yup is widely used in the React ecosystem, especially with form libraries like Formik.

README

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