Add class one by one using jquery

Add class one by one using jquery

$("ul li").on('click' , function () {
  setInterval(function(){
    var el = $('.main_div');
      var index = 0;
        var timer = window.setInterval(function(){
          if  (index < el.length) {
            el.eq(index++).addClass('highlighted');
          } else {
          window.clearInterval(timer);
        }
    }, 1000);
  }, 1);
});