setInterval & setTimeout timer function do not work within portal pagelet

My environment is portal 9.1 feature pack 3 on Tools 8.54.09

There is content references that set the cookie by iscript when a user click a button. Another pagelet ( on the same tab ) is supposed to check if cookie has been set on interval (every 1 second). In this pagelet, I am using plain javascript to check the value of the cookie.

While building the setup, I am puzzeed by the javascript timer functions (setInterval & setTimeout) not working within pagelet.

This following command would work fine on any web server but it would not work if it is been placed inside a pagelet when data type is either 'free text' or 'html'.