README.md

json-schema

This package provides a TypeScript and JavaScript implementation of JSON Schema validation. In particular, it does so with the following goals:

• High performance. Internally, this package pre-compiles schemas, and allocates these pre-compiled schemas in an arena to reduce memory use and improve cache locality.
• Running untrusted schemas. This package will never download schemas from the network, nor fetch them from a local filesystem. Furthermore, you can tell this package to abort early if it appears that a schema is defined cyclically.
• Control over number of errors returned. If you are only interested in knowing whether a schema is valid or not, you can have this package stop evaluation on the first error. If you're presenting errors to users, you can also limit the number of errors to some sensible amount.

Documentation

You can find detailed documentation at:

https://json-schema-spec.github.io/json-schema-typescript/

Usage

Create a validator using the Validator constructor. Then, evaluate instances using the validate method:

import { Validator } from "@json-schema-spec/json-schema";

const schema = {
  properties: {
    name: {
      type: "string",
      minLength: 3,
    },
    age: {
      type: "integer",
    },
  },
};

const instance = {
  name: "ab" // note: this name is too short
  age: "thirty seven", // note: this age is of the wrong type
};

const validator = new Validator([schema]);
const result = validator.validate(instance);

console.log(result.isValid()) // Outputs: false

for (const error of result.errors) {
  console.log(`validation error at ${error.instancePath} (due to: ${error.schemaPath})`);
}

// Outputs:
// validation error at /name (due to: /properties/name/minLength)
// validation error at /age (due to: /properties/age/type)

The returned errors are guaranteed to be valid JSON Pointers, returned from the @json-schema-spec/json-pointer package, so you can easily get ahold of what part of your schema or instance the error came from, if the path isn't enough.