I was recently involved in the TypeScript migration of the ZK Framework. For those who are new to ZK, ZK is the Java counterpart of the Node.js stack; i.e., ZK is a Java full-stack web framework where you can implement event callbacks in Java and control frontend UI with Java alone. Over more than a decade of development and expansion, we have reached a code base of more than 50K JavaScript and over 400K Java code, but we noticed that we are spending almost the same amount of time and effort in maintaining Java and JavaScript code, which means, in our project, JavaScript is 8 times harder to maintain than Java.
I would like to share the reason we made the move to migrate from JavaScript to TypeScript, the options we evaluated, how we automated a large part of the migration, and how it changed the way we work and gave us confidence.