Add class to html tag using jquery

Question

I got this html code:

<form id = "xxx">
   <ul>
     <li class = "req" > </li>
     <li class = "req" > </li>
     <li class = "req" > </li>
     <li > </li>    ==================> HOW CAN I ADD A CLASS="req" to this li with jquery
     <li class = "req" > </li>
     ....
    <li class = "req" > </li>
  </ul>
</form>

So, I rewrite the question: is there an li tag that does not have (class = "req"), how can I add this using jquery? Thanks you

Answer 1

$("#xxx li").addClass("req");

.

If you want to explicitly add it only to liwithout req, you can do:

$("#xxx li:not(.req)").addClass("req");

If you want to add a class only to the fourth element, follow these steps:

$("#xxx li:eq(3)").addClass("req");

3lies in the fact that it uses a zero index for elements.

Answer 2

If you cannot check if the element has a specific attr.

$("ul#yourid").not(".req").addClas("req");

Answer 3

jQuery('li').addClass('req');