As JavaScript applications get more and more complex, improved performance is on everyone's minds. In the meantime, computers are evolving: CPU hardware is scaling with multi-core, big.LITTLE rather than frequency. Where does JavaScript stand in this new world and how can it adapt? What role will WebAssembly play in this? What are the current tools and techniques developers can use to develop performant JavaScript applications and what is in store for the future? These are the few questions that we will answer in the course of this presentation.