Emerging consumer electronics products are running the same software platforms that power smartphones. This leads to the appealing idea that a uniform programming abstraction can be used for app development for a range of devices, from wearables to smartphones. In practice, however, devices vary in their hardware capabilities and this has an impact on app development. In this talk, we will present an ahead-of-time compiler for a rich subset of JavaScript that enables more efficient execution on resource-constrained devices. A novel type system ensures a predictable performance model, and a global type inference technique significantly reduces the effort required to port existing code.