Sitecore JSS allows for full use of the Sitecore Experience Platform (XP) feature set
There are lots of great reasons to choose a Sitecore JSS site. From a software development perspective, Sitecore JSS embraces the most modern development practices and paradigms. Sitecore JSS features many different development modes, and sites can be developed with our without Sitecore installed on the developer's machine. Sitecore JSS solutions are also great for marketing and content managers as well. Sitecore's content management, layout manipulation, experience editor, and analytics features are all available for use.
Sitecore JSS sites allow for experiences in the browser that are more interactive than traditional server side rendered websites. The user can be pushed new content without refreshing the page or clicking on any links. Functionality such as sports score updates, new promotion announcements, and live chat functionality are just some examples of things that can be done with JSS.
JSS is available for all Sitecore installations as of Sitecore 9.0. JSS is versioned independently from Sitecore, with version 12.0 being the most current version at the time of writing of this article. Your Sitecore license file will need support for JSS.
Can a JSS site live alongside my existing Sitecore site?
Absolutely. There are multiple strategies that can be taken to begin developing JSS powered content on your Sitecore site. As Sitecore has support for multiple sites in one instance, a JSS site can be spun up alongside your existing SXA or traditional sites. With the right content architecture approach, content could be configured to be shared between JSS and traditional sites. Sitecore also offers support to integrate JSS functionality into existing non-headless sites if a more piecemeal approach is desired.
How do I get started with JSS?