> For the complete documentation index, see [llms.txt](https://valantic.gitbook.io/spartacus-mock/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://valantic.gitbook.io/spartacus-mock/examples/define-handlers.md).

# Define Handlers

You can define custom handlers for your custom endpoints or for existing endpoints (aka OCC Endpoints) of spartacus-mock.

1. Create a handlers file `src/mock-server/handlers.ts`
2. Create a folder `src/mock-server/mock-data` where all your mock-data lives
3. In the handlers file you can define all your custom handlers like in this example:

```ts
// src/mock-server/handlers.ts
import { getDefaultRoutes } from '@valantic/spartacus-mock';
import {
  HttpHandler,
  HttpResponse,
  PathParams,
  StrictRequest,
  http,
} from 'msw';
import { environment } from '../environments/environment';
import { countryList } from './mock-data/countries';

// default routes defined in the spartacus-mock library
// for custom routes, use your getRoutes function explained above
const defaultRoutes = getDefaultRoutes(environment);

export const handlers = (): RestHandler[] => {
  return [
    http.get<{}, { foo: number; bar: string }>(
      defaultRoutes.languages,
      ({ request, params }) => {
        return HttpResponse.json(languageList());
      }
    ),
  ];
};
```

> Defining a custom handler for an existing route (aka OCC Endpoint) will override the default handler for this route.

4. Create a file `src/mock-server/mock-data/languages.ts`
5. Add a `languageList` function to return the mock-data for the languages endpoint:

```ts
// src/mock-server/mock-data/languages.ts
import { createLanguage } from '@valantic/spartacus-mock';
import { Occ } from '@spartacus/core';

// you can use the `createLanguage` function from our library or create your own
export const languageList = (): Occ.LanguageList => {
  return {
    languages: [
      createLanguage({
        isocode: 'en',
        name: 'English',
        nativeName: 'English',
      }),
      createLanguage({
        isocode: 'de',
        name: 'German',
        nativeName: 'Deutsch',
      }),
    ],
  };
};
```

6. Append your handlers to the mockConfig in your `main.ts` file

```ts
// src/main.ts
// your custom defined handlers
import { handlers } from './mock-server/handlers';

async function prepare(): Promise<
  ServiceWorkerRegistration | undefined
> {
  if (environment.mockServer) {
    const { prepareMock } = await import(
      /* webpackChunkName: "mock-server" */ '@valantic/spartacus-mock'
    );

    const mockConfig: MockConfig = {
      enableWorker: environment.mockServer || false,
      environment,
      handlers: handlers(),
    };

    return prepareMock(mockConfig);
  }

  return Promise.resolve(undefined);
}
```