TOP MOBILE APP DEVELOPMENT FRAMEWORKS IN 2019

React Native - Open Source; Free

Highlights:

1. Reusability: React Native was originally developed by Facebook to design the user interface of its mobile application. In the beginning, the React Native framework only worked with iOS.
2. Efficiency: The benefits of React, such as high performance and a virtual DOM, carry over to React Native as well. Using React Native can make you more efficient and speed up your development times in a variety of ways.
3. JavaScript: JavaScript has risen from its lowly origins to become the king of web programming languages. Nearly everyone calling themselves a "web developer” has had a good deal of experience with JavaScript.

Native Script - Open Source; Free

Highlights:

1. Native cross-platform mobile applications using JavaScript, TypeScript or Angular.
2. Directly access all native platform APIs on both iOS and Android.
3. NativeScript framework exposes unmodified native APIs and UI components allowing you to use the latest native APIs and UI components immediately once released from Apple, Google or Microsoft in one of their platform updates.

Flutter - Open Source; Free

Highlights:

1. Developed and used by Google.
2. Heavily optimized, mobile-first 2D rendering engine with excellent support for text.
3. Command-line tools that allow for building, creating, testing, and compiling.
4. React-style framework.
5. Lots of widgets for Android and iOS.
6. Unit and integration tests APIs.
7. Third-party SDKs and Interop and plugin APIs to connect to the system.
8. Headless test runner for Windows, Linux, and Mac.

Xamarin - Open Source; Free

Highlights:

1. Native user-interface & controls that allow you to create a native app.
2. Cross-platform app development.
3. Included with Visual Studio.
4. Easy API Integration.
5. Access Native APIs.

Ionic - Open Source; Free

Highlights:

1. Easy adoption.
2. Cross-platform app development.
3. User Interface.
4. Built on AngularJS.
5. Performance.
6. Cordova Plugins.

Adobe PhoneGap - Open Source; Free

Highlights:

1. Uses only HTML, CSS, and JavaScript.
2. Makes use of network protocols (XmlHTTPRequest, Web Sockets, etc) to communicate with backend services.
3. Reuse existing business processes and APIs.
4. Based upon the open source Apache Cordova project.

Apache Cordova - Open Source; Free

Highlights:

1. Uses HTML5, CSS3, and JavaScript for cross-platform development.
2. Incorporates standards-compliant API bindings to access each device's capabilities such as sensors, data, network status, etc.

Corona SDK - Open Source; Free

Highlights:

1. Publish to all major platforms from a single code base.
2. Over 1000 APIs available to tap into.
3. Lua-based codebase.
4. Corona Simulator offers a real-time preview of your app.
5. Live Build also offers a real-time testing solution.
6. Apps are automatically compiled at build time, allowing optimum performance and stability.

Intel XDK - If you search for "top mobile app development frameworks" in 2019, you will still find the top contenders referencing Intel XDK as a top choice. Yes, it was good while it lasted, but time to update that this is no longer available on Intel's site everyone. It has been discontinued.