export_postprocess.js

const replace = require('replace-in-file'); // https://www.npmjs.com/package/replace-in-file
const path = require('path');

const scriptName = path.basename(process.argv[1]);

const options = {
  files: [
    'out/*.html',
    'out/**/*.html',
  ],
  from: [
    /<link rel="preload" href="\/_next\/[^\/]+\/[^.]+\.js" as="script"\/>/g,
    /(<script.+<\/script>)(<\/div>)*<\/body><\/html>/, // optional `</div>`: appears in next.js 4.2.1 but not in 4.3.0-canary.1
  ],
  to: [
    '',
    (match, p1, p2) => {
      let output = `<script>
setTimeout(function(){
var insertScript = function (src, id) {
  var scriptEl = document.createElement('script');
  id && (scriptEl.id = id);
  scriptEl.src = src;
  document.body.appendChild(scriptEl);
}
`;
      const scripts = p1.split('</script>');
      let i, l, matches;
      for (i = 0, l = scripts.length; i < l; i++) {
        if (!scripts[i]) continue;
        output += `  insertScript('` + scripts[i].match(/ src="([^"]+)"/)[1] + `'`;
        matches = scripts[i].match(/ id="([^"]+)"/);
        if (matches) {
          output += `, '` + matches[1] + `'`;
        }
        output += `);\n`;
      }
      return output + `}, 0);\n</script>` + (p2 || '') + `</body></html>`;
    },
  ],
};

replace(options)
  .then(changes => {
    console.log(scriptName + ': modified files:', changes.join(', '));
  })
  .catch(error => {
    console.error(scriptName + ': error occurred:', error);
  });