Halibut said:
I've been using react native professionally for about a year and a half. 90% of your code will work on both platforms. The other 10% is stuff that is platform specific like push notifications, permissions management, and the actual app deployment process.
Note that it's a JavaScript framework that builds UIs using the native platform's UI manager. So you get the native app look/feel, but you don't necessarily have to learn Java and Swift/Objective C. (There are some edge cases where you might have to write native code though.)
Yep I built an app on a local LAMP stack using HTML5, CSS, and javascript on the client side and, php, mysql on the back end then ported it using hosting from Go Daddy. The thing runs on ANY OS or platform running a modern browser. Unless you are accessing client side hardware or local drivers you dont need to use Java, Swift or Objective C.
This is not an approach for every application but it sure works on a bunch of 'em. And these tools can get you productive quickly but be prepared to study and put in the time.