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The "Unexpected default export of anonymous function" warning is caused when we try to export an anonymous function using default export. To fix the error, name the function before exporting it.

The following is a sample code that produces the above error

Header.js

// 👇️ default export for anonymous function

// ⛔️ Unexpected default export of anonymous function
// eslint import/no-anonymous-default-export
export default function () {
  return <h1>hello world</h1>;
}

The problem here is that we are using default export to export the anonymous function.

To fix the error, name the function before using the default export.

Header.js

// 👇️ give name to function that's being exported
export default function Header() {
  return <h1>hello world</h1>;
}

Important: If we export a variable (or arrow function) as a default export, we must declare it on the first line and export it on the next line. We cannot declare and default export a variable on the same line.

Header.js

const Header = () => {
  return <h1>hello world</h1>;
};

export default Header;

Now we can still import functions using default import.

App.js

import Header from './Header';

const App = () => (
  <div>
    <Header />
  </div>
);

export default App;

This approach encourages reusing the same identifiers when exporting and importing functions.

By default, eslint rules will warn us about anonymous default exports of all types, such as arrays, functions, classes, objects, etc.

If you want to disable a single line rule, you can use comment.

Header.js

// eslint-disable-next-line import/no-anonymous-default-export
export default function () {
  return <h1>hello world</h1>;
}

The comment should be placed just above the code with the anonymous default export.

Optionally, we can update what import/no-anonymous-default-exportthe rule should .eslintrccheck for in the file.

The options section of the Github repository shows the full default configuration for the rule, which we can .eslintrctweak in the rule object in our ./configure file.

Summarize

The "Unexpected default export of anonymous function" warning is caused when we try to export an anonymous function using default export. To fix the error, name the function before exporting it.