Next.js Advanced Interview Questions

Published on 6 Nov, 2020

Question

What is Preview Mode in Next.js? How does it help?

Answer

Preview mode helps to preview a web page before it is actually published. For example, if Next.js is showing product details page in an eCommerce website, the business team might need to preview before publishing a new product. So Next.js creates static pages for all published products and shows the preview page dynamically when requested.

Question

What are API Routes in Next.js?

Answer

API routes helps developer to create APIs using Next.js. API routes are defined inside pages/api folder.

Question

Inside pages/api folder in Next.js, we created a file about.js with following code.

function About() {
  return <h1>About page</h1>;
}

export default About;

Assume that our app is running on http://localhost:3000, what will be the output when we visit http://localhost:3000/api/about?

Answer

We cannot see the About component. All endpoints under /api should resolve by sending back a response explicitly. In this case, we see a page which will be loading forever.