Jquery-Ui : Highlight effect inside iframe using Firefox

Question

I am trying to do the highlight effect using Firefox.

The element is inside of an iframe. My code works with Chrome but not with Firefox.

To catch the content, I use :

var iframeContent = $(window.frames[0].document.documentElement);
var elem = $(iframeContent).find("#something");

Then, I use the effect like that :

$(elem).effect("highlight", {}, 2000); 

I call my effect after every "onLoad" event. Once iframe and document are loaded.

How can I do ?

Thanks.

EDIT : I added an example : https://jsfiddle.net/yr1h9fdz/10/