Am I thinking wrong or right please help me to find out.

Question

I was thinking about 'how Zomato and Swiggy actually work and if someone wants to build such kind of application can he built it by just using React.js or he has to learn server side scripting language as well.

The most important thing he want to know is how it shows the nearest restaurant as search results, and how much time will it take to build such app if he doesn't know much about backend.