Remove last comma from array.foreach

Hi,

As you can see at Images ,i want to remove the last comma from  the loop .

Hovewer don't know how to do it.

this is the script ;

var year = LISTBOX_1.getSelectedTexts ();

var y = " ";

year.forEach(function(element, index)

{

y = y + element + ", ";

TEXT_1 = setText(y);

}

);

Regards,

Erdem