json-schema-to-typescript

v15.0.3

Published

a month ago

compile json schema to typescript typings

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bcherny

json schema typescript compile transpile api interface typing share

json-schema-to-typescript

Compile JSON Schema to TypeScript typings.

Example

Check out the live demo.

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

npm install json-schema-to-typescript

Usage

json-schema-to-typescript is easy to use via the CLI, or programmatically.

CLI

First make the CLI available using one of the following options:

# install locally, then use `npx json2ts`
npm install json-schema-to-typescript

# or install globally, then use `json2ts`
npm install json-schema-to-typescript --global

# or install to npm cache, then use `npx --package=json-schema-to-typescript json2ts`
# (you don't need to run an install command first)

Then, use the CLI to convert JSON files to TypeScript typings:

cat foo.json | json2ts > foo.d.ts
# or
json2ts foo.json > foo.d.ts
# or
json2ts foo.yaml 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 below (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

API

To invoke json-schema-to-typescript from your TypeScript or JavaScript program, import it and call compile or compileFromFile.

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 | |-|-|-|-| | additionalProperties | boolean | true | Default value for additionalProperties, when it is not explicitly set | | bannerComment | string | "/* eslint-disable */\n/**\n* This file was automatically generated by json-schema-to-typescript.\n* DO NOT MODIFY IT BY HAND. Instead, modify the source JSON Schema file,\n* and run json-schema-to-typescript to regenerate this file.\n*/" | Disclaimer comment prepended to the top of each generated file | | customName | (LinkedJSONSchema, string \| undefined) => string \| undefined | undefined | Custom function to provide a type name for a given schema | 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? | | inferStringEnumKeysFromValues | boolean | false | Create enums from JSON enums with eponymous keys | | 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. | | maxItems | number | 20 | Maximum number of unioned tuples to emit when representing bounded-size array types, before falling back to emitting unbounded arrays. Increase this to improve precision of emitted types, decrease it to improve performance, or set it to -1 to ignore maxItems. | strictIndexSignatures | boolean | false | Append all index signatures with \| undefined so that they are strictly typed. | | 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 $defs that aren't referenced by the schema. | | $refOptions | object | {} | $RefParser Options, used when resolving $refs |

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] deprecated
[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