json-schema-to-typescript

Compile json schema to typescript typings

Example

Input:

{
  "title": "Example Schema",
  "type": "object",
  "properties": {
    "firstName": {
      "type": "string"
    },
    "lastName": {
      "type": "string"
    },
    "age": {
      "description": "Age in years",
      "type": "integer",
      "minimum": 0
    },
    "hairColor": {
      "enum": ["black", "brown", "blue"],
      "type": "string"
    }
  },
  "additionalProperties": false,
  "required": ["firstName", "lastName"]
}

Output:

export interface ExampleSchema {
  firstName: string;
  lastName: string;
  /**
   * Age in years
   */
  age?: number;
  hairColor?: "black" | "brown" | "blue";
}

Installation

# Using Yarn:
yarn add json-schema-to-typescript

# Or, using NPM:
npm install json-schema-to-typescript --save

Usage

import { compile, compileFromFile } from 'json-schema-to-typescript'

// compile from file
compileFromFile('foo.json')
  .then(ts => fs.writeFileSync('foo.d.ts', ts))

// or, compile a JS object
let mySchema = {
  properties: [...]
}
compile(mySchema, 'MySchema')
  .then(ts => ...)

See server demo and browser demo for full examples.

Options

compileFromFile and compile accept options as their last argument (all keys are optional):

| key | type | default | description | |-|-|-|-| | bannerComment | string | "/* tslint:disable */\n/**\n* This file was automatically generated by json-schema-to-typescript.\n* DO NOT MODIFY IT BY HAND. Instead, modify the source JSONSchema file,\n* and run json-schema-to-typescript to regenerate this file.\n*/" | Disclaimer comment prepended to the top of each generated file | | cwd | string | process.cwd() | Root directory for resolving $refs | | declareExternallyReferenced | boolean | true | Declare external schemas referenced via $ref? | | enableConstEnums | boolean | true | Prepend enums with const? | | format | boolean | true | Format code? Set this to false to improve performance. | | ignoreMinAndMaxItems | boolean | false | Ignore maxItems and minItems for array types, preventing tuples being generated. | | style | object | { bracketSpacing: false, printWidth: 120, semi: true, singleQuote: false, tabWidth: 2, trailingComma: 'none', useTabs: false } | A Prettier configuration | | unknownAny | boolean | true | Use unknown instead of any where possible | | unreachableDefinitions | boolean | false | Generates code for definitions that aren't referenced by the schema. | | strictIndexSignatures | boolean | false | Append all index signatures with \| undefined so that they are strictly typed. | | $refOptions | object | {} | $RefParser Options, used when resolving $refs |

CLI

A CLI utility is provided with this package.

cat foo.json | json2ts > foo.d.ts
# or
json2ts foo.json > foo.d.ts
# or
json2ts foo.json foo.d.ts
# or
json2ts --input foo.json --output foo.d.ts
# or
json2ts -i foo.json -o foo.d.ts
# or (quote globs so that your shell doesn't expand them)
json2ts -i 'schemas/**/*.json'
# or
json2ts -i schemas/ -o types/

You can pass any of the options described above (including style options) as CLI flags. Boolean values can be set to false using the no- prefix.

# generate code for definitions that aren't referenced
json2ts -i foo.json -o foo.d.ts --unreachableDefinitions
# use single quotes and disable trailing semicolons
json2ts -i foo.json -o foo.d.ts --style.singleQuote --no-style.semi

Tests

npm test

Features

• [x] title => interface
• [x] Primitive types:
  • [x] array
  • [x] homogeneous array
  • [x] boolean
  • [x] integer
  • [x] number
  • [x] null
  • [x] object
  • [x] string
  • [x] homogeneous enum
  • [x] heterogeneous enum
• [x] Non/extensible interfaces
• [ ] Custom JSON-schema extensions
• [x] Nested properties
• [x] Schema definitions
• [x] Schema references
• [x] Local (filesystem) schema references
• [x] External (network) schema references
• [x] Add support for running in browser
• [x] default interface name
• [x] infer unnamed interface name from filename
• [x] allOf ("intersection")
• [x] anyOf ("union")
• [x] oneOf (treated like anyOf)
• [x] maxItems (eg)
• [x] minItems (eg)
• [x] additionalProperties of type
• [x] patternProperties (partial support)
• [x] extends
• [x] required properties on objects (eg)
• [ ] validateRequired (eg)
• [x] literal objects in enum (eg)
• [x] referencing schema by id (eg)
• [x] custom typescript types via tsType

Custom schema properties:

• tsType: Overrides the type that's generated from the schema. Useful for forcing a type to any or when using non-standard JSON schema extensions (eg).
• tsEnumNames: Overrides the names used for the elements in an enum. Can also be used to create string enums (eg).

Not expressible in TypeScript:

• dependencies (single, multiple)
• divisibleBy (eg)
• format (eg)
• multipleOf (eg)
• maximum (eg)
• minimum (eg)
• maxProperties (eg)
• minProperties (eg)
• not/disallow
• oneOf ("xor", use anyOf instead)
• pattern (string, regex)
• uniqueItems (eg)

FAQ

JSON-Schema-to-TypeScript is crashing on my giant file. What can I do?

Prettier is known to run slowly on really big files. To skip formatting and improve performance, set the format option to false.

Further Reading

• JSON-schema spec: https://tools.ietf.org/html/draft-zyp-json-schema-04
• JSON-schema wiki: https://github.com/json-schema/json-schema/wiki
• JSON-schema test suite: https://github.com/json-schema/JSON-Schema-Test-Suite/blob/node
• TypeScript spec: https://github.com/Microsoft/TypeScript/blob/master/doc/spec.md

Who uses JSON-Schema-to-TypeScript?

• AWS, AWSLabs
• FormatJS
• Microsoft
• Sourcegraph
• Stryker
• Webpack
• See more