not_has example

HTML

<ul>
  <li>A</li>
  <li>B</li>
  <li>C<span>x</span></li>
  <li>D<span>y</span></li>
  <li>E</li>
  <li>F<span>z</span></li>
</ul>

<a class="add-span" href="#">check</a>

JavaScript

(function ( $ ) {
    $.fn.extend({
        not_has: function (param) {
            return this.not(this.has(param));
        }
    });
}( jQuery ));

$("a.add-span").click(function() {
    $("li").not_has("span")
    .append('<span class="spn">new span<\/span>');
    
    // Prevents the page from navigating away
    return false;
});