Edit in JSFiddle

$('li').html(function(i){
    return 'my index is - ' + i;
});

<ul id="foo">
    <li class="other">Beef Jerky</li>
    <li>Smoked Salmon</li>
    <li class="other">Rocky Mountain Oysters</li>
    <li class="other">Beef Jerky</li>
    <li>Smoked Salmon</li>
    <li class="other">Rocky Mountain Oysters</li>
</ul>