plugin for generating types for Express route handlers

Usage no npm install needed!

<script type="module">
  import dtsgeneratorExpressRouteTypes from 'https://cdn.skypack.dev/dtsgenerator-express-route-types';



This is a dtsgenerator plugin for generating types for Express route handlers.

For each route specified under the Paths namespace, this plugin will look for types (PathParameters, Responses, RequestBody and QueryParameters) that are defined for that path, and use unknown (or any) for those types that can't be found.

For example, for a path like DeletePet (note it doesn't defined types for query parameters and body payload):

declare namespace Paths {
  namespace DeletePet {
      namespace Parameters {
          export type Id = number;
      export interface PathParameters {
          id: Parameters.Id;
      namespace Responses {
          export type Default = Components.Schemas.Error;

and a config object like:

    "placeholderType": "any",
    "routeTypeName": "RouteHandler",

the plugin would add the following types:

type RouteHandler = RequestHandler<Paths.DeletePet.PathParameters, Paths.DeletePet.Responses.Default, unknown, unknown>;

interface RouteConfig {
    pathParams: Paths.DeletePet.PathParameters; // { id: number }
    responses: Paths.DeletePet.Responses.Default;
    successResponses?: unknown;
    requestBody?: unknown;
    queryParams?: unknown;
    headers?: unknown;

RouteHandler type

The RouteHandler type can be used to add static type checking to a route's path parameters, query parameters, body payload, and responses. For example:

const app = express(); // Invoke express to variable for use in application
const route: Paths.DeletePet.RouteHandler = (req, res, next) => {
  req.params.id; // OK. also, `id` is of type `number`
  req.params.name; // NOK, `name` is not a valid param
  res.status(500).json({ message: '33434' }); // OK
  res.status(500).json("something went wrong"); // NOK, `Components.Schemas.Error` does not allow a string
  // the same would happen with `req.query` and `req.body`

RouteConfig type

The RouteConfig interface is more flexible, and can be used to add static type checking to both server and client implementations.

The fields of this type will be optional and unknown whenever they don't apply to that specific route. For example, the DeletePet route from the example above doesn't specify any query parameters, so the queryParams field is optional.

This interface has the following fields:

  • pathParams is be an object with a field for each of the route's path parameters (e.g., for /example/{id}, could be an object with type {id: number})
  • responses is a union type with all valid responses for the route (both successes and failures)
  • sucessResponses is also a union type, but only contains types for... success responses (there is typically only one of those).
  • requestBody is the type of the request body
  • queryParams is be an object with a field for each of the route's query parameters (e.g., for /example?userId=123&company=abc, could be an object with type {userId: number, company: string})
  • headers is an object with a field for each of the route's headers


npm install dtsgenerator-express-route-types


The configuration object for the plugin takes two parameters:

  • placeholderType specifies which type should be used when the type for some parameter isn't defined. Only unknown and any are supported
  • routeTypeName specifies the name of the type that the plugin creates


    "plugins": {
        "dtsgenerator-express-route-types": {
            "placeholderType": "unknown", // or "any"
            "routeTypeName": "Route", // whatever name you want for the express request handler type


npm run build
npm test


  • TypeScript
  • eslint
  • prettier

npm scripts

main scripts

  • npm run build: transpile this plugin. This command need before publishing this plugin.
  • npm test: test this plugin with coverage.

sub scripts

  • npm run watch: watch editing files for compile.
  • npm run lint:fix: fix lint error automatically.
  • npm run test:update-snapshot: update snapshot files for unit test.
  • npm run coverage: report to coveralls. Need coveralls configuration file.