At FINN oppdrag, a year ago we came to realize that our front-end code, written in JSP/jQuery, had become so large and complex that it affected our ability to produce features. We spent more time making sure the DOM manipulations were correct and did not break, than actually creating value for our users.
Our attraction to React was based on its promise of providing components with encapsulated state, fast automatic DOM manipulations, and the ability to render on the server.
We started by porting some functionality that already existed, and our first discovery was that the lines of codes needed to make the exact same functionality was almost reduced by half. Secondly, the code became clearer and easier to understand. And thirdly, as a combination of the reduced lines of code, the cleaner code and no manual DOM manipulations, we got less bugs.
Since then all new features have been written with React, and when we are requested to make modifications to functionality written in the old code, we rewrite them to use React.
When migrating large pages to React we start from the inside, the deepest DOM nodes, and let it gradually grow till the whole page is reactified. This often happened through several iterations and deployments, as React and the old JSP/JQuery can quite peacefully coexist.
So if React is our first great discovery, the Flux pattern is very much in second place. The Flux pattern decouples the logic from the views, in a different way than the traditional MVC-pattern. Logic and state are located in stores, and actions from the views to stores are asynchronous. When state in stores change, they will update React components that listen to changes, providing a single source of truth and unidirectional flow of data.
All these three solutions have their own benefits and challenges.
So, apart from server-side rendering, which we are working on, our transition to React has been smooth and a great success. It has improved our codebase, made developers happy, and most importantly, improved our speed of delivering features, which in the end is the most important thing.