Understanding Data Fetching in Nextjs

Introduction

In a Next.js application, data fetching is a crucial operation allowing you to manipulate and display data from different sources like APIs, databases, or even local files. This tutorial will discuss the various data fetching methods that Next.js provides out of the box. We'll cover the getStaticProps, getServerSideProps, and getInitialProps functions, exploring what they are, how they work, and when to use each.

What is Data Fetching?

Data fetching in Next.js refers to the process of retrieving data that your application needs to render its components. This could be from an API, a database, or any other data source. The data can be fetched at different stages of the application lifecycle, either at build time, on each request, or on the client-side after the page has been rendered.

Static Generation: getStaticProps

getStaticProps is a Next.js data fetching function that you can use to fetch data at build time. It runs on the server-side and is ideal when you want to generate static pages ahead of a user's request. This function should return an object having a props key, and the value should be an object containing data that you want to pass to your page.

export async function getStaticProps(context) {
  const res = await fetch(`https://.../data`)
  const data = await res.json()

  return {
    props: {
      data,
    },
  }
}

Server-side Rendering: getServerSideProps

If you need to fetch data at request time instead of at build time, getServerSideProps is the function to use. This function runs on each request, ideal for pages that need server-side rendering. Like getStaticProps, getServerSideProps also returns an object with a props key.

export async function getServerSideProps(context) {
  const res = await fetch(`https://.../data`)
  const data = await res.json()

  return {
    props: {
      data,
    },
  }
}

Client-side Rendering: getInitialProps

For fetching data on the client side after a page has rendered, Next.js provides the getInitialProps function. This function is ideal when your data changes frequently and you don't need to pre-render the page. However, it disables automatic static optimization for the page.

MyPage.getInitialProps = async (context) => {
  const res = await fetch(`https://.../data`)
  const json = await res.json()
  return { data: json }
}

Conclusion

Understanding when and how to fetch data is crucial in Next.js applications. Whether you're building a blog, an eCommerce store, or any other type of application, you'll need to fetch data from somewhere. By understanding getStaticProps, getServerSideProps, and getInitialProps, you're well on your way to mastering data fetching in Next.js.

Each method has its own use case and depending on the frequency of how much your data updates, you can make a mindful decision on which method to use. Remember, Next.js is all about performance and user experience. Choose wisely based on your application's needs.