A 30 minute talk is far too short to give a highly detailed explanation on writing code transformations, but hopefully serves as a nice introduction:
If you want to play with codemods yourself:
- JSCodeShift provides an API to write code transformations, and a CLI tool to apply them to your code base.
- AST Explorer is a great tool to discover what an Abstract Syntax Tree (AST) looks like, and also lets you write codemods in the same screen (which makes writing and testing them a breeze).
- reactjs/react-codemod and cpojer/js-codemod contain a lot of useful codemods that can help get you started.