# E0224: TypeScript type annotations are not allowed in JavaScript code

JavaScript variables and function returns cannot be explicitly typed with an annotation:

    async function fetchJSON(uri: string): Promise<any> {
      let req: Response = await fetch(uri);
      return await req.json();
    }

To fix this error, rename your file to have a `.ts` or `.tsx` suffix.

Alternatively, use JSDoc to write the annotations:

    /**
     * @param {string} uri
     * @returns {Promise<any>}
     */
    async function fetchJSON(uri) {
      /** @type {Response} */
      let req = await fetch(uri);
      return await req.json();
    }

Introduced in quick-lint-js version 2.6.0.

Documentation for other errors