将Class添加到每个第二个元素，从第一个元素开始计数

Question

I have a list where I want to add classes to every second element, counting from the first one.

Here's my list

<ul class="timeline">
  <span class="topbullet"></span>
  <li></li>
  <li></li>
  <div class="clearfix"></div>
  <li></li>
  <li></li>
  <div class="clearfix"></div>
  <li></li>
  <li></li>
  <div class="clearfix"></div>
  <li></li>
  <li></li>
  <div class="clearfix"></div>
  <li></li>
  <li></li>
  <div class="clearfix"></div>
</ul>

I want to have it like this:

<ul class="timeline">
  <span class="topbullet"></span>
  <li class="odd"></li>
  <li class="even"></li>
  <div class="clearfix"></div>
  <li class="odd"></li>
  <li class="even"></li>
  <div class="clearfix"></div>
  <li class="odd"></li>
  <li class="even"></li>
  <div class="clearfix"></div>
  <li class="odd"></li>
  <li class="even"></li>
  <div class="clearfix"></div>
  <li class="odd"></li>
  <li class="even"></li>
  <div class="clearfix"></div>
</ul>

Here's my jQuery Code

$(".timeline li:nth-of-type(2n)").addClass('even');

It's no problem to add the 'even' classes, but how to add the 'odd' classes? Which selector should I use to count from the first list element?

Answer 1

You can use odd and even selector of jquery like this

$( ".timeline li:odd" ).addClass('odd');
$( ".timeline li:even" ).addClass('even');

For your requirement you need to first odd and than even so you change this jquery like this

$( ".timeline li:odd" ).addClass('even');
$( ".timeline li:even" ).addClass('odd');

Answer 2

Or JUST this

document.body.querySelectorAll(".timeline li").forEach(function(node,i){
   node.classList.add(i % 2?"even":"odd");
})

Answer 3

You could do this:
Iterate through the elements matching ".timeline li" and add the correct class whether its index is even or not.

$(".timeline li").each((index, el) => $(el).addClass(index % 2 ? 'even' : 'odd'));

Answer 4

Just simply add prev() method to your code:

 $(".timeline li:nth-of-type(2n)").addClass('even').prev().addClass('odd'); 

 .even{ color:red; } .odd{ color: orange; } 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <ul class="timeline"> <span class="topbullet">Span</span> <li>Li</li> <li>Li</li> <div class="clearfix">Div</div> <li>Li</li> <li>Li</li> <div class="clearfix">Div</div> <li>Li</li> <li>Li</li> <div class="clearfix">Div</div> <li>Li</li> <li>Li</li> <div class="clearfix">Div</div> <li>Li</li> <li>Li</li> <div class="clearfix">Div</div> </ul> 

Answer 5

Change:

$(".timeline li:nth-of-type(2n)").addClass('even');

to:

    $(".timeline li:nth-child(even)").addClass('even');

Answer 6

If you just want to style elements you can target them using css

.timeline li:nth-of-type(2n + 1) {
    background: red;
}
.timeline li:nth-of-type(2n) {
    background: blue;
}

Answer 7

You can add odd/even class like the below example.

 $(document).ready(function() { $('ul.listul li:even').addClass('even'); $('ul.listul li:odd').addClass('odd'); }); 

 li.even { color: #000; } li.odd { color: red; } 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <ul class="listul"> <li>list1</li> <li>list2</li> <li>list3</li> <li>list4</li> <li>list5</li> <li>list6</li> </ul>