bendecoste / swagger-js

Javascript library to connect to swagger-enabled APIs via browser or nodejs

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This is the new version of swagger-js, 3.x. Want to learn more? Check out our FAQ.

For the older version of swagger-js, refer to the 2.x branch.


The npm package is called swagger-client and the GitHub repository is swagger-js. We'll be consolidating that soon. Just giving you the heads up. You may see references to both names.


  • Runtime:
    • browser: es5 compatible. IE11+
    • node v4.x.x
  • Building
    • node v6.x.x
Download via npm
npm install swagger-client
Import in code
import Swagger from 'swagger-client'
// Or commonjs
const Swagger = require('swagger-client')
Import in browser
<script src='browser/swagger-client.js' type='text/javascript'></script>
var swaggerClient = new SwaggerClient(specUrl);


This lib exposes these functionalities:

  • Static functions for...
    • HTTP Client
    • Swagger Spec Resolver ( OAS 2.0 )
    • TryItOut Executor
  • A constructor with the methods...
    • HTTP Client, for convenience
    • Swagger Spec Resolver ( OAS 2.0 ), which will use url or spec from the instance
    • TryItOut Executor, bound to the http and spec instance properties
    • Tags Interface, also bound to the instance

HTTP Client

Swagger.http(req) exposes a Fetch-like interface with a twist: allowing url in the request object so that it can be passed around and mutated. It extends Fetch to support request and response interceptors and performs response & header serialization. This method could be overridden to change how SwaggerJS performs HTTP requests.

// Fetch-like, but support `url`, `query` and `xxxInterceptor`
const request = {

  .then((res) => {
    res.statusCode // status code
    res.statusText // status text, ie: "Not Found"
    res.body       // JSON object or undefined
    res.obj        // same as above, legacy
    res.text       // textual body, or Blob
    res.headers    // header hash
  .catch((err) => {
    err            // instanceof Error
    err.response   // response or null

// Interceptors
  requestInterceptor: (req: Request) => Request | Promise<Request>
  responseInterceptor: (res: Response) => Response | Promise<Response>

// Custom Fetch
  userFetch: (url: String, options: Object) => Promise

Swagger Specification Resolver

Swagger.resolve({url, spec, http}) resolves $refs (JSON-Refs) with the objects they point to.

Swagger.resolve({url, spec, http}).then((resolved) => {
  resolved.errors // resolution errors, if any
  resolved.spec   // the resolved spec

This is done automatically if you use the constructor/methods

TryItOut Executor

An HTTP client for OAS operations, maps an operation and values into an HTTP request.

const params = {

  operationId, // Either operationId, or you can use pathName + method

  parameters, // _named_ parameters in an object, eg: { petId: 'abc' }
  securities, // _named_ securities, will only be added to the request, if the spec indicates it. eg: {apiKey: 'abc'}

  (http), // You can also override the HTTP client completely
  (userFetch), // Alternatively you can just override the fetch method (if you want to use request.js or some other HttpAgent)

// Creates a request object compatible with HTTP client interface.
// If `pathName` and `method`, then those are used instead of operationId. This is useful if you're using this dynamically, as `pathName` + `method` are guarenteed to be unique.
const res = Swagger.execute({...params})

// You can also generate just the request ( without executing... )
const req = Swagger.buildRequest({...params})

Constructor and methods

Resolve the spec and expose some methods that use the resolved spec:

  • Swagger(url, opts): Promise
  • Exposes tags interface (see above)
  • Exposes the static functions: execute, http, resolve and some other minor ones
  • Exposes #http, #execute and #resolve bound to the instance
  .then( client => {
      client.spec // The resolved spec
      client.originalSpec // In case you need it
      client.errors // Any resolver errors

      // Tags interface{id: 1, name: "bobby"}).then(...)

      // TryItOut Executor, with the `spec` already provided
      client.execute({operationId: 'addPet', parameters: {id: 1, name: "bobby") }).then(...)

Tags Interface

A client for operations. We're currently using the apis[tag][operationId]:ExecuteFunction interface, which can be disabled entirely using Swagger({disableInterfaces: true}) if you don't need it.

OperationId's are meant to be unique within spec, if they're not we do the following:

  • If a tag is absent, we use default as the internal tag
  • If an operationId is missing, we deduce it from the http method and path, i.e. ${method}${path}, with non-alphanumeric characters escaped to _. See these tests (1, 2) for examples.
  • If an operationId is duplicated across all operationIds of the spec, we rename all of them with numbers after the ID to keep them unique. You should not rely on this, as the renaming is non-deterministic. See this test for an example.
Swagger({ url: "" }).then((client) => {
      .pet // tag name == `pet`
      .addPet({ // operationId == `addPet`
        id: 1,
        body: {
          name: "bobby",
          status: "available"

If you'd like to use the operationId formatting logic from Swagger-Client 2.x, set the v2OperationIdCompatibilityMode option:

  url: "",
  v2OperationIdCompatibilityMode: true
}).then((client) => {
  // do things as usual

OpenAPI 3.0

OpenAPI 3.0 definitions work in a similar way with the tags interface, but you may need to provide additional data in an options object for server variables and request bodies, since these items are not actual parameters:

Swagger({...}).then((client) => {
      .pet // tag name == `pet`
      .addPet({ // operationId == `addPet`
        id: 1
      }, {
        requestBody: {
          name: "bobby",
          status: "available"
        server: "{apiPrefix}/", // this should exactly match a URL in your `servers`
        serverVariables: {
          apiPrefix: "v2"

In Browser

Prepare swagger-client.js by npm run build-bundle Note, browser version exports class SwaggerClient to global namespace If you need activate CORS requests, just enable it by withCredentials property at http

<script src='browser/swagger-client.js' type='text/javascript'></script>

var specUrl = ''; // data urls are OK too 'data:application/json;base64,abc...'
SwaggerClient.http.withCredentials = true; // this activates CORS, if necessary

var swaggerClient = new SwaggerClient(specUrl)
      .then(function (swaggerClient) {
          return{id: 1, name: "bobby"}); // chaining promises
      }, function (reason) {
         console.error("failed to load the spec" + reason);
      .then(function(addPetResult) {
         // you may return more promises, if necessary
      }, function (reason) {
          console.error("failed on API call " + reason);
  check console in browser's dev. tools


SwaggerJS has some legacy signature shapes.


Response shape
// swagger-js

  data, // The textual content
  obj   // The body object

// New shape
  headers, // See note below regarding headers

  text,    // The textual content
  body,    // The body object
Serializing Headers

By default the instance version of #http serializes the body and headers. However, headers pose an issue when there are multiple headers with the same name. As such we've left the static version of http to not perform any serialization.


npm install
npm run test         # run test
npm run test:watch   # run test with change watching
npm run lint         # run lint
npm run build        # package to release
npm run build-dev    # package with non-minified dist/index.js (for debugging)
npm run build-bundle # build browser version available at .../browser

Migration from 2.x

There has been a complete overhaul of the codebase. For notes about how to migrate coming from 2.x, please see Migration from 2.x

Security contact

Please disclose any security-related issues or vulnerabilities by emailing, instead of using the public issue tracker.


For features known to be missing from 3.x please see the Graveyard


Javascript library to connect to swagger-enabled APIs via browser or nodejs



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