Does Window have focus

if (document.hasFocus())
  console.log('Has focus')

Trigger on page load

  window.addEventListener('pageshow', function() {    //'pageshow' triggers for page load and back button back to page
    
  });

      //jQuery(window).on('load', function() {      //This won't trigger if user presses their back button
      jQuery(window).on('pageshow', function() {    //'pageshow' triggers for page load and back button back to page

      });

Trigger on page got focus

  window.addEventListener('focus', function()
  {
    
  });
//Won't trigger for 'pageshow', use a separate window.addEventListener('pageshow' function for that