OATS for JavaScript

import { getSchema, getSchemaJson, SCHEMA_VERSION } from "oatschema";const schema = getSchema("classification"); // a new plain object on every callschema.$id; // "https://oatschema.org/0.8.0/classification"getSchemaJson("classification"); // the file's text, exactly as releasedSCHEMA_VERSION; // "0.8.0", used when you don't pass a version

The schemas are embedded in the module, so the package works the same in Node.js, browsers, Deno, Bun and any bundler. It ships as ESM with TypeScript types, and schema names are a union type, so typos fail at compile time. Each schema is byte-identical to its release on this site.

The package has no validator of its own: getSchema returns a plain object for any JSON Schema draft 2020-12 validator. With Ajv:

import Ajv2020 from "ajv/dist/2020.js";import addFormats from "ajv-formats";import { getSchema } from "oatschema";const ajv = new Ajv2020({ allErrors: true, strictTypes: false, strictTuples: false, strictRequired: false });ajv.addKeyword({ keyword: "x-license", schemaType: "object" });ajv.addKeyword({ keyword: "x-version", schemaType: "string" });addFormats(ajv);const validate = ajv.compile(getSchema("classification"));validate({ labels: [{ label: "cat", score: 0.92 }] }); // truevalidate({ labels: [{ label: "cat", score: 1.5 }] }); // falsevalidate.errors; // [{ instancePath: "/labels/0/score", message: "must be <= 1", ... }]

• x-license and x-version are the only non-standard keywords in OATS. Registering them keeps Ajv's strict mode on for everything else.
• The three relaxed options switch off Ajv's style checks, which reject some valid draft 2020-12 patterns that OATS uses, such as required inside an if.
• Compile each schema once per Ajv instance and reuse the function. Compiling a second copy with the same $id throws; fetch the first with ajv.getSchema(schema.$id).

Before OATS 1.0, a new release may reject records an older one accepted, or the reverse, so pass the version a record was written for: getSchema("classification", "0.8.0").

• version must be exact: "0.8.0", never "0.8" or "latest".
• Each $id includes its version, so several versions can share one Ajv instance.
• The package bundles OATS 0.8.0, the first public release, and every later one. For 0.4.0 to 0.7.0, use the Python package, or fetch them from this site.

More on releases in Versions and URLs.

The package has its own semantic version, which never encodes a schema version; read SCHEMA_VERSION instead. Upgrading never removes a schema version, but it can move the default. Before 1.0, a release that changes the default is a minor bump, so npm's default ^0.x.y range keeps your default fixed.