albertpak/_document.js

## _document.js
// In case anyone else needs this, here's what I done to add FB Messenger code to my NextJS app - As mentioned before, you need to drop the plugin code into `_document.js` and modify `script` tag

import Document, { Html, Head, Main, NextScript } from 'next/document';

export default class MyDocument extends Document {
  render() {
    return (
      <Html>
        <Head>
          {/* code that you want to add to the header */}
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
        <div id="fb-root"></div>
        <script
          dangerouslySetInnerHTML={{
            __html: `
            window.fbAsyncInit = function() {
              FB.init({
                xfbml            : true,
                version          : 'v10.0'
              });
            };

            (function(d, s, id) {
              var js, fjs = d.getElementsByTagName(s)[0];
              if (d.getElementById(id)) return;
              js = d.createElement(s); js.id = id;
              js.src = 'https://connect.facebook.net/en_US/sdk/xfbml.customerchat.js';
              fjs.parentNode.insertBefore(js, fjs);
            }(document, 'script', 'facebook-jssdk'));
            `,
          }}
        />

        <div className="fb-customerchat"
          attribution="page_inbox"
          page_id="YOUR_FB_PAGE_ID">
        </div>
      </Html>
    )
  }
}
	// In case anyone else needs this, here's what I done to add FB Messenger code to my NextJS app - As mentioned before, you need to drop the plugin code into `_document.js` and modify `script` tag

	import Document, { Html, Head, Main, NextScript } from 'next/document';

	export default class MyDocument extends Document {
	render() {
	return (
	<Html>
	<Head>
	{/* code that you want to add to the header */}
	</Head>
	<body>
	<Main />
	<NextScript />
	</body>
	<div id="fb-root"></div>
	<script
	dangerouslySetInnerHTML={{
	__html: `
	window.fbAsyncInit = function() {
	FB.init({
	xfbml : true,
	version : 'v10.0'
	});
	};

	(function(d, s, id) {
	var js, fjs = d.getElementsByTagName(s)[0];
	if (d.getElementById(id)) return;
	js = d.createElement(s); js.id = id;
	js.src = 'https://connect.facebook.net/en_US/sdk/xfbml.customerchat.js';
	fjs.parentNode.insertBefore(js, fjs);
	}(document, 'script', 'facebook-jssdk'));
	`,
	}}
	/>

	<div className="fb-customerchat"
	attribution="page_inbox"
	page_id="YOUR_FB_PAGE_ID">
	</div>
	</Html>
	)
	}
	}