We use XCode for compiling our Javascript to iOS. We do that using Cordova/PhoneGap, a bridge technology that runs the javascript in a dedicated UIWebView on iOS. Doing so suffers a performance penalty because we're running interpreted code instead of native, so it's often a bit sluggish compared to native apps. We're looking forward to see how much WebAssembly can improve on things; and until then, we focus on having real clean UI code. If all the components are functional, tested, don't have side-effects, and are non-blocking, then even the interpret code can feel like a native app. It takes a lot of discipline to write clean Javascript code that can do that, though. Lastly, we use the Meteor pipeline to launch XCode as a build step.