After a few years using Kotlin in production for server development, we were confident in the quality of the language, the dedicated team at JetBrains and the overall long-term support. So when kotlin.js was announced as production ready, we decided to start a new project for data visualization based on Kotlin. Choosing Kotlin was a bet on the future for a real multi-platform data visualization tool while leveraging the power given by Kotlin’s ability to create internal DSL’s. Even if kotlin.js was "production ready" in March, we had to find the best development workflows. This talk gives you feedback on our journey, the technical challenges we faced and how we resolved them: * why Kotlin on the front end? * which workflows for development, tests, and packaging? * debugging kotlin.js, * optimizing the produced javascript, * integration with existing javascript libraries, * feedback on kotlin.js performances. Gaetan Zoritchak is an enthusiastic father, developer, entrepreneur, paraglider pilot, … Having used lots of languages during his 20 years of IT experience, he believed very early on in the promises of Kotlin. He started in 2012 to code with it and in 2013 to promote it as a speaker.