<title>My Example</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
$( "button" ).click( function() {
$( "li" ).not( ":odd" ).fadeOut( "slow" );
<button>Fade out the even list items (i.e. the "non-odd" ones)</button>
<p>Even ones start at the first list item (zero-based indexing).</p>