Hi Hariharan,
Thanks so much for your question - you may actually find this previous forum thread on Creating Test on pages with React js
helpful, specifically: that according to the Target Product Documentation on at.js Implementation , although at.js communicates with the Target servers asynchronously, the at.js file itself must load synchronously in the <head> section of your page. Ideally, it should be one of the first scripts loaded. Once loaded, at.js executes mbox calls asynchronously through XMLHttpRequest, and does not block page rendering." Hope this is helpful - feel free to reach out here again if you have more questions!
Warmly,
Amelia