simple example of how to run js code that was meant to run in a browser context from node

client-code.js

document.addEventListener('DOMContentLoaded', function() {
  console.log(window.location.protocol);
});

server-code.js

const fs = require('fs');

const clientCode = fs.readFileSync('client-code.js', 'utf8');

const fakeLocation = { protocol: 'https:' };
const fakeWindow = { location: fakeLocation };

const fakeDocument = { addEventListener: (type, callback) => callback() }

const globals = {
  window: fakeWindow,
  document: fakeDocument
};

runClientScript(clientCode, globals);

function runClientScript(source, globals) {
  const globalKeys = Object.keys(globals);
  const globalValues = Object.values(globals);

  const fn = new Function(globalKeys, source);
  fn.apply(fakeWindow, globalValues);
}