Refactoring React applications on a massive scale is a different beast. What to do when “find and replace” simply isn’t enough? We faced this challenge when we needed to unify the way React was used across an application consisting of hundreds of components. This is a story about how we created a faultless commit that touched around 100,000 lines of code. Our solution was to write a program that did the required modifications for us. These kind of programs are often called codemods. Languages and concepts are like tools in a toolbox. Codemods are a new tool to your toolbox.