If you want to parse files within the same server you should probably use some of this options, because nodejs it's just a JavaScript implementation, There is no window or document object, see this.   But to answer exactly your question: 
how can I use document.getElementById() in nodejs ?
You could do it using Puppeteer
Puppeteer is a Node library which provides a high-level API to control
  headless Chrome or Chromium over the DevTools Protocol. It can also be
  configured to use full (non-headless) Chrome or Chromium.
Here a basic example:
const puppeteer = require('puppeteer');
(async () => {
    const browser = await puppeteer.launch();
        page = await browser.newPage();
        await page.goto('http://example.com/some.html', {waitUntil: 'load'});
    const newPage = await page.evaluate(() => {
        return  document.getElementById("idexample").innerHTML;
        });
     console.log(newPage)
  })();