# E0213: TypeScript's 'interface' feature is not allowed in JavaScript code

JavaScript does not support interfaces. It is a syntax error to write a TypeScript interface in JavaScript code:

    interface Response<T> {
      ok: boolean;
      error?: string;
      data?: T;
    }

To fix this error, rename your file to have a `.ts` or `.tsx` suffix. Alternatively, use JSDoc to declare the interface:

    /**
     * @typedef {Object} Response
     * @prop {boolean} ok
     * @prop {string} [error]
     * @prop {Object} data
     */

Introduced in quick-lint-js version 2.5.0.

Documentation for other errors