Insightful Summary of ESLint v9.0.0 Release

The release of ESLint v9.0.0 marks a significant update for the JavaScript linter. It introduce essential changes that enhance functionality and improve user experience.

This version incorporates several new features, addresses numerous bugs from previous versions, and introduces breaking changes that developers need to be aware of.

Key updates in ESLint v9.0.0 include the adoption of flat config as the default configuration format, replacing the traditional .eslintrc files.

This shift simplifies the configuration process and aligns ESLint with modern development practices.

Developers looking to maintain the .eslintrc format can still do so by setting an environment variable.

Another major enhancement is the introduction of the no-useless-assignment rule, designed to identify and report instances where assigned variables are not utilized effectively, helping developers optimize their code.

The removal of certain formatters and rules like valid-jsdoc and require-jsdoc reflects ESLint’s move towards a more streamlined tool, encouraging the use of more specialized plugins for these purposes.

This version also discontinues support for older versions of Node.js (prior to v18.18.0 and v19), therefore you might need to update to more recent versions to maintain compatibility and security.

What challenges did you encounter upgrading to ESLint v9.0.0?

https://eslint.org/blog/2024/04/eslint-v9.0.0-released/