Which is better (WordPress Or ReactJs) for Ecommerce Application?

If you need to launch soon and have the skills and knowledge, you can create a store with ReactJS.

However, keep in mind that is is only the front end, you need to have a database like MongoDB, or choose a SQL db.

Decide on the stack you will use. In your case, take a look at the MERN stack.

I hope you know Node.js and Express.js.

Don't forget to make it responsive, so it looks good on mobile devices and is optimized for search engines and for speed.

You need to host your react.js web app online, and I would suggest either AWS or Google cloud.

Once it is up, you need to explore and decide on a payment processing company, like PayPal or Stripe.

Those are a few things you need to think about and be ready for.

All the best!

Ps. WordPress maybe easier but you need to be on top of your game in terms of security and need to know PHP.