PolymerJS is another open-source JavaScript library for using web components to make web applications. Developed by Google developers and released on GitHub, Polymer Js is designed to imitate the features present on the web platform to build components.
It’s the best library to introduce interactive application structuring by compiling components. It is being used by Google services and many other platforms. The popularity of PolymerJS in the market can be attributed to its structured design procedures i.e. the components.
The very reason they have strengthened support for web components and have outstanding offline modules in comparison with React. Read More here