Hi All, Can we use react js in our application??

Yes, but since the application is backed by Backbone MVVM architecture, it will be a lot more work to to integrate a new front-end framework. Just FYI, External Catalog Site (WSDK) gives you the flexibility to use your own website, while taking advantage of NetSuite shopping cart and checkout capabilities. Ref: https://netsuite.custhelp.com/app/answers/detail/a_id/27642