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	note
cwd	string	Root directory for resolving $refs
declareExternallyReferenced	boolean	Declare external schemas referenced via $ref?
enableConstEnums	boolean	Prepend enums with const?
style	object	A Prettier configuration
unreachableDefinitions	boolean	Generates code for definitions that aren't referenced by the schema.

CLI

A simple 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

Tests

npm test

Todo

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

Not expressible in TypeScript:

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

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