openapi-typescript

What is openapi-typescript?

The openapi-typescript npm package is a tool that generates TypeScript types from OpenAPI specifications. This helps developers ensure type safety and better integration between their API definitions and TypeScript code.

What are openapi-typescript's main functionalities?

Generate TypeScript Types

This feature allows you to generate TypeScript types from an OpenAPI specification URL. The generated types are then saved to a file named 'types.ts'.

const openapiTS = require('openapi-typescript');
const fs = require('fs');

async function generateTypes() {
  const types = await openapiTS('https://api.example.com/openapi.json');
  fs.writeFileSync('types.ts', types);
}

generateTypes();

Generate Types from Local File

This feature allows you to generate TypeScript types from a local OpenAPI specification file. The generated types are saved to a file named 'types.ts'.

const openapiTS = require('openapi-typescript');
const fs = require('fs');
const path = require('path');

async function generateTypes() {
  const types = await openapiTS(path.join(__dirname, 'openapi.json'));
  fs.writeFileSync('types.ts', types);
}

generateTypes();

Custom Type Generation Options

This feature allows you to customize the type generation process by providing options such as a transform function. The transform function can be used to modify the schema before generating the types.

const openapiTS = require('openapi-typescript');
const fs = require('fs');

async function generateTypes() {
  const types = await openapiTS('https://api.example.com/openapi.json', {
    transform: (schema) => {
      // Custom transformation logic
      return schema;
    }
  });
  fs.writeFileSync('types.ts', types);
}

generateTypes();

Other packages similar to openapi-typescript

swagger-typescript-api

The swagger-typescript-api package generates TypeScript API client code from Swagger/OpenAPI definitions. It provides more advanced features like generating API client methods and supports both Swagger 2.0 and OpenAPI 3.0 specifications.

typescript-fetch

The typescript-fetch package is a generator for TypeScript clients using the Fetch API. It generates TypeScript code from OpenAPI specifications and is particularly useful for creating client-side code that interacts with RESTful APIs.

README

openapi-typescript turns OpenAPI 3.0 & 3.1 schemas into TypeScript quickly using Node.js. No Java/node-gyp/running OpenAPI servers necessary.

The code is MIT-licensed and free for use.

Tip: New to OpenAPI? Speakeasy’s Intro to OpenAPI is an accessible guide to newcomers that explains the “why” and “how” of OpenAPI.

Features

• ✅ Supports OpenAPI 3.0 and 3.1 (including advanced features like discriminators)
• ✅ Generate runtime-free types that outperform old school codegen
• ✅ Load schemas from YAML or JSON, locally or remotely
• ✅ Generate types for even huge schemas within milliseconds

Note: OpenAPI 2.x is supported with versions 5.x and previous

Examples

👀 See examples

Setup

This library requires the latest version of Node.js installed (20.x or higher recommended). With that present, run the following in your project:

npm i -D openapi-typescript typescript

And in your tsconfig.json, to load the types properly:

{
  "compilerOptions": {
+    "module": "ESNext", // or "NodeNext"
+    "moduleResolution": "Bundler" // or "NodeNext"
  }
}

Highly recommended

Also adding the following can boost type safety:

{
  "compilerOptions": {
+    "noUncheckedIndexedAccess": true
  }
}

Basic usage

First, generate a local type file by running npx openapi-typescript, first specifying your input schema (JSON or YAML), and where you’d like the --output (-o) to be saved:

# Local schema
npx openapi-typescript ./path/to/my/schema.yaml -o ./path/to/my/schema.d.ts
# 🚀 ./path/to/my/schema.yaml -> ./path/to/my/schema.d.ts [7ms]

# Remote schema
npx openapi-typescript https://myapi.dev/api/v1/openapi.yaml -o ./path/to/my/schema.d.ts
# 🚀 https://myapi.dev/api/v1/openapi.yaml -> ./path/to/my/schema.d.ts [250ms]

Then in your TypeScript project, import types where needed:

import type { paths, components } from "./my-openapi-3-schema"; // generated by openapi-typescript

// Schema Obj
type MyType = components["schemas"]["MyType"];

// Path params
type EndpointParams = paths["/my/endpoint"]["parameters"];

// Response obj
type SuccessResponse =
  paths["/my/endpoint"]["get"]["responses"][200]["content"]["application/json"]["schema"];
type ErrorResponse =
  paths["/my/endpoint"]["get"]["responses"][500]["content"]["application/json"]["schema"];

From here, you can use these types for any of the following (but not limited to):

• Using an OpenAPI-supported fetch client (like openapi-fetch)
• Asserting types for other API requestBodies and responses
• Building core business logic based on API types
• Validating mock test data is up-to-date with the current schema
• Packaging API types into any npm packages you publish (such as client SDKs, etc.)

📓 Docs

View Docs