Next.js: Reduce data fetching and share data between pages

O’right! I found this thread while I was looking for something else. But since I had to work on similar issues, I can give you some directions, and I will do my best to make it clear for you.

So there are some data which you want to have it share, across your app (pages/components).

1. Next.js uses the App component to initialize pages. You can override it and control the page initialization. to achieve that simply create _app.js file in root of pages directory. For more information follow this link: https://nextjs.org/docs/advanced-features/custom-app
2. Just like the way you can use getInitialProps in your pages to fetch data from your API, you can also use the same method in _app.js. So, I would fetch those data which I need to share them across my app and eliminate my API calls.

Well, Now I can think of two ways to share the data across my app

1. Using of createContext hooks.

1.1. Create a DataContext using createContext hooks. and wrap <Component {...pageProps} /> with your <DataContext.Provider>.
Here is a code snippet to give you a better clue:

<DataContext.Provider value={{ userData, footerData, etc... }}>
  <Component {...pageProps} />
</DataContext.Provider>

1.2. Now in other pages/components you can access to your DataContext like following:

const { footerData } = useContext(DataContext); 

And then you are able to do the manipulation in your front-end

2. populates props using getInitialProps

2.1. getInitialProps is used to asynchronously fetch some data, which then populates props. that would be the same case in _app.js.

The code in your _app.js would be something like this:

function MyApp({ Component, pageProps, footerData }) {
  //do other stuffs
  return (
   <Component {...pageProps} footerData={footerData} />
  ;
}

MyApp.getInitialProps = async ({ Component, ctx }) => {
  const footerRes = await fetch('http://API_URL');
  const footerData = await footerRes.json(); 
  let pageProps = {};
  if (Component.getInitialProps) {
    pageProps = await Component.getInitialProps(ctx);
  }
  return { pageProps, footerData };
};

2.2. Now in your pages (not in your components) you can access to props including those you have shared from _app.js
and you can start to do you manipulation.

Hope I could give you a clue and direction. Have fun exploring.