var x = document.getElementsByClassName("eg-lceco1-element-32"); var i; var sep = "-"; for (i = 0; i < x.length; i++) { var str =x[i].innerHTML.toString(); var res = str.slice(0, 4); var res2 = str.slice(4, 6); var res3 = str.slice(6, 8); x[i].innerHTML = res.concat(sep, res2, sep, res3); }