JS判斷頁面是否為瀏覽器當前頁

function currentPage() {
  var hiddenProperty = 'hidden' in document ? 'hidden' :
    'webkitHidden' in document ? 'webkitHidden' :
      'mozHidden' in document ? 'mozHidden' :
        null;
  var visibilityChangeEvent = hiddenProperty.replace(/hidden/i, 'visibilitychange');
  var onVisibilityChange = function () {
    if (!document[hiddenProperty]) {
      console.log('頁面激活');

    } else {
      console.log('頁面非激活')

    }
  }
  document.addEventListener(visibilityChangeEvent, onVisibilityChange);
}