Edit in JSFiddle

var $foo = $('li');

// this implicitly calls .first()
console.log('Index: ' + $foo.index("li")); // 0
console.log('Index: ' + $foo.first().index("li")); // 0

var $baz = $('#baz1');
console.log('Index: ' + $baz.index("li")); // 2

var $listItem = $('#bar1');
console.log('Index: ' + $listItem.index(".test")); // 1

var $div = $('#last');
console.log('Index: ' + $div.index("div")); // 2