Discover how to tackle large-scale JavaScript refactoring in this 28-minute conference talk from AmsterdamJS December 2018 Meetup. Learn about codemods, powerful tools for automated code modifications, as the speaker shares their experience of unifying React component initial state setting across thousands of files. Explore the concept of Abstract Syntax Trees (AST) and how to leverage them for efficient refactoring. Gain insights into the process of creating a transformation that affected around 100,000 lines of code, including testing strategies and potential challenges. Ideal for developers looking to enhance their refactoring skills and streamline large-scale codebase modifications.