import { ServerStyleSheets } from '@material-ui/core' import Document, { Html, Head, Main, NextScript } from 'next/document' import { Children } from 'react' class MyDocument extends Document { render() { return (
) } } export default MyDocument // `getInitialProps` belongs to `_document` (instead of `_app`), // it's compatible with server-side generation (SSG). MyDocument.getInitialProps = async (ctx) => { // Resolution order // // On the server: // 1. app.getInitialProps // 2. page.getInitialProps // 3. document.getInitialProps // 4. app.render // 5. page.render // 6. document.render // // On the server with error: // 1. document.getInitialProps // 2. app.render // 3. page.render // 4. document.render // // On the client // 1. app.getInitialProps // 2. page.getInitialProps // 3. app.render // 4. page.render // Render app and page and get the context of the page with collected side effects. const sheets = new ServerStyleSheets() const originalRenderPage = ctx.renderPage ctx.renderPage = () => originalRenderPage({ enhanceApp: (App) => (props) => sheets.collect(), }) const initialProps = await Document.getInitialProps(ctx) return { ...initialProps, // Styles fragment is rendered after the app and page rendering finish. styles: [ ...Children.toArray(initialProps.styles), sheets.getStyleElement(), ], } }