All the pages on your site look more or less the same. There’s a chrome, a common base layer, and you just want to change what’s inside.

There’s a nav bar, a sidebar, and then the actual content.

How do you build such system in Next.js?

There are 2 ways. One is using a Higher Order Component, by creating a components/Layout.js component:

export default Page => {
  return () => (
    <div>
      <nav>
        <ul>....</ul>
      </nav>
      <main>
        <Page />
      </main>
    </div>
  )
}

In there we can import separate components for heading and/or sidebar, and we can also add all the CSS we need.

And you use it in every page like this:

import withLayout from '../components/Layout.js'

const Page = () => <p>Here's a page!</p>

export default withLayout(Page)

But I found this works only for simple cases, where you don’t need to call getInitialProps() on a page.

Why?

Because getInitialProps() gets only called on the page component. But if we export the Higher Order Component withLayout() from a page, Page.getInitialProps() is not called. withLayout.getInitialProps() would.

To avoid unnecessarily complicating our codebase, the alternative approach is to use props:

export default props => (
  <div>
    <nav>
      <ul>....</ul>
    </nav>
    <main>
      {props.content}
    </main>
  </div>
)

and in our pages now we use it like this:

import Layout from '../components/Layout.js'

const Page = () => (
  <Layout content={(
    <p>Here's a page!</p>
  )} />
)

This approach lets us use getInitialProps() from within our page component, with the only downside of having to write the component JSX inside the content prop:

import Layout from '../components/Layout.js'

const Page = () => (
  <Layout content={(
    <p>Here's a page!</p>
  )} />
)

Page.getInitialProps = ({ query }) => {
  //...
}

Lessons in this unit:

0:	Introduction
1:	Absolute imports in Next.js
2:	How to change a Next.js app port
3:	Next.js, adding features just to development mode
4:	Next.js how to show something in development and hide in production
5:	▶︎ Adding a wrapper component to your Next.js app