TypeError: null is not an object (evaluating 'document.body.insertBefore')

[matiasmacera]

Im getting this error when trying to add the script

TypeError: null is not an object (evaluating 'document.body.insertBefore')

[youcanping]

script in body is OK

[sandoche]

Try loading the library with a function on window's load:

  function addDarkmodeWidget() {
    new Darkmode().showWidget();
  }
  window.addEventListener('load', addDarkmodeWidget);