This utility type will extract the schema properties definition from a valid JSONSchema7 object into a TypeScript type.

ExtractProperties.ts

import { JSONSchema7 } from 'json-schema';

type StringToType = {
  string: string;
  boolean: boolean;
  number: number;
  integer: number;
  null: null;
  object: object;
  array: object;
};

type StringToTypeIndex<Property> = Property extends keyof StringToType
  ? StringToType[Property]
  : never;

type ValidateIsJSONSchema7<Schema> = Schema extends JSONSchema7
  ? Schema
  : never;

export type ExtractProperties<
  Schema extends JSONSchema7
> = Schema['type'] extends 'object'
  ? {
      [Property in keyof Schema['properties']]: ExtractProperties<
        ValidateIsJSONSchema7<Schema['properties'][Property]>
      >;
    }
  : Schema['type'] extends 'array'
  ? Array<ExtractProperties<ValidateIsJSONSchema7<Schema['items']>>>
  : StringToTypeIndex<Schema['type']>;

// Example
const foo = {
  properties: {
    foo: {
      type: 'object' as const,
      properties: {
        baz: {
          type: 'boolean' as const,
        },
      },
    },
    bar: { type: 'string' as const },
  },
};
  
type Foo = ExtractProperties<typeof foo>;
/**
 * typeof Foo = {
 *   foo: {
 *     baz: boolean;
 *   },
 *   bar: string;
 * }
 */