How can I make the script work only on one page?

Question

JavaScript

Tell me how to make the script work only on one specific page?

It is necessary so that on all pages there is no error about not finding a class or ID.

Script:

const headerWindow = document.getElementById('header_window'),
    openHeaderWindow = document.getElementById('control_avatar'),
    closeHeaderWindow = document.getElementsByClassName('close_window')[0];

openHeaderWindow.onclick = function () {
  headerWindow.style.display = 'block';
}
closeHeaderWindow.onclick = function () {
  headerWindow.style.display = 'none';
}
window.onclick = function(e) {
  if (e.target == headerWindow) {
    headerWindow.style.display = 'none';
  }
}

Screenshot of the error on the other pages:

Answer 1

Check if there is such a selector on the page and then execute the code

Answer 2

Make sure that this script is present only on the desired page, and not on the rest.

Answer 3

if( !headerWindow ) return