https://takao.blog/en/tags/eslint/Recent content in Eslint on Commentary of TakaoHugo -- gohugo.ioenCommentary of TakaoSat, 13 Jun 2026 23:11:50 +0900https://takao.blog/en/web/eslint-flat-config/Mon, 26 Feb 2024 00:00:00 +0900https://takao.blog/en/web/eslint-flat-config/<img src="https://takao.blog/img/thumnail.webp" alt="Featured image of post ESLint Flat Config: Migration Guide from Legacy .eslintrc" /><p>ESLint v9.0, released in 2024, made the flat config system (<code>eslint.config.js</code>) the default, replacing the legacy <code>.eslintrc</code> format that had been in use for over a decade. This migration guide covers the complete transition process, new concepts, and practical examples.</p> <h2 id="why-flat-config">Why Flat Config? </h2><p>The legacy <code>.eslintrc</code> system had several problems: configuration cascading made behavior unpredictable, directory-based resolution was complex, JSON/YAML lacked support for functions and comments, and shareable configs were difficult to compose. Flat config addresses these with a single configuration file, explicit composition via JavaScript arrays, simplified plugin resolution, and full JavaScript-native syntax.</p>