Again and again I see young developers asking the same question and making the same mistake.
Technology stack for businesses is like politics for engineers.
In other words - it doesn't matter. Moreover, you can't answer that question without more information about a project.
Business requirements, budget and a team experience first > tech stack second and never vice versa.
Only those questions will determine a tech stack:
If you goal is to have fun, build own project and not a business, and you want to dicover something new, then again, it doesn't matter. Take whatever you don't know and jump into it.
For mobile apps - native tools always should be used, i.e. Swift 3 for iOS and not hybrid crazy JS everywhere.
For back-end I am using PHP7 because it was made for that simple use case and because I am working with it for almost ten years. For front-end I am using vanilla JS (ES6 now) since it is a powerful and simple tool to script the browser and it is the only way to "speak to browser". With solid knowledge of these technologies you can move mountains and you are always flexible, may add as many abstraction, frameworks and libraries on top of it any time.
Mev-Rael
Executive Product Leader & Mentor for High-End Influencers and Brands @ mevrael.com