Parsing Lexical to HTML gives empty string

Question

I am using a lexical editor and want to convert lexical data to HTML on click of a button.

After referring from this question, I am using $generateHtmlFromNodes and wrapping it inside editor.update function.

My code:

import { $generateHtmlFromNodes } from '@lexical/html';

document.getElementById("export-html").addEventListener("click", () => {
    editor.update(() => {
      const htmlString = $generateHtmlFromNodes(editor, null);
      console.log('htmlString', htmlString);
    });
  }) 

The output I am receiving: enter image description here

Expecting a proper HTML output in string format. I checked Serialization as well.