Zod

Zod is a TypeScript-first schema declaration and validation library. I'm using the term "schema" to broadly refer to any data type, from a simple string to a complex nested object.

Zod is designed to be as developer-friendly as possible. The goal is to eliminate duplicative type declarations. With Zod, you declare a validator once and Zod will automatically infer the static TypeScript type. It's easy to compose simpler types into complex data structures.

Some other great aspects:

• Zero dependencies
• Works in Node.js and all modern browsers
• Tiny: 8kb minified + zipped
• Immutable: methods (e.g. .optional()) return a new instance
• Concise, chainable interface
• Functional approach: parse, don't validate
• Works with plain JavaScript too! You don't need to use TypeScript.