How to add a class for html tag () depending a condition with javascript

I need to add style classes according to the number of <span> in a <li> I start with the following code:

$(document).ready(function() {
    var ul = document.getElementsByTagName("ul");
for (var i, li; li = ul.childNodes[i]; i++) {
    if (li.tagName == 'LI') {
        var container = li.getElementsByTagName("span");
        var nb = container.length;
            if (nb == 1) 
        {
            container[0].childNodes[0].setAttribute("class", "class1")
        } 
            else if (nb == 2) 
        {
            container[0].childNodes[0].setAttribute("class", "class2")
            container[0].childNodes[1].setAttribute("class", "class3")
        }
    }
}});

JsFiddle Example