genson-js

genson-js

genson-js is a user-friendly JSON Schema generator built in TypeScript/JavaScript.

This is not the JavaScript equivalent of the Java Genson library. The motivation for this library was to port GenSON python library to JS, however having exactly the same api or possiblities was not a goal.

genson-js's core function is to take JSON objects and generate schemas that describe them, with an ability to merge schemas.

Usage

Creating schemas

To infer a schema from existing object:

import { createSchema } from 'genson-js';

const schema = createSchema({
    userName: 'smith',
    languages: ['c++', 'java'],
    age: 40,
});

// will create the following schema:
// {
//   type: "object",
//   properties: {
//     userName: {
//       type: "string",
//     },
//     languages: {
//       type: "array",
//       items: {
//         type: "string",
//       },
//     },
//     age: {
//       type: "integer",
//     },
//   },
//   required: ["userName", "languages", "age"],
// };

Merging schemas

You can merge 2 schemas, so that merged schema would be kind of a superset of the schemas that it was built from:

import { mergeSchemas } from 'genson-js';

const merged = mergeSchemas([{ type: ValueType.Number }, { type: ValueType.String }]);

// will create merged schema like this:
// { type: ['number', 'string'] }

Exending schemas

You can extend existing schema to match some value:

import { extendSchema } from 'genson-js';

const extended = extendSchema({ type: ValueType.Number }, 'string');

// will create extended schema like this:
// { type: ['number', 'string'] }

Comparing schemas

You can extend compare 2 schemas for equality like this:

import { areSchemasEqual } from 'genson-js';

areSchemasEqual({ type: ValueType.Number }, { type: ValueType.Number });
// will return true

Subset

You can also check if one schema is a subset of another one like so:

You can extend compare 2 schemas for equality like this:

import { isSubset } from 'genson-js';

isSubset(
    { type: ValueType.Array, items: { type: [ValueType.Boolean, ValueType.Integer] } },
    { type: ValueType.Array, items: { type: [ValueType.Boolean] } }
);
// will return true

You can find more example in the unit tests.