如果你想在同一时间添加它并向下滑动这个：

If you wanted it to be added and slide down at the same time do this:

function prependListItem(listName, listItemHTML){
    $(listItemHTML).hide().prependTo('#' + listName).slideDown('slow');
}

要真正做到你所描述的（向下滑动，然后淡入），你需要这样的东西：

To truly do exactly what you described (slide down, then fade in), you would need something like this:

function prependListItem(listName, listItemHTML){
    $(listItemHTML)
        .hide()
        .css('opacity',0.0)
        .prependTo('#' + listName)
        .slideDown('slow')
        .animate({opacity: 1.0})
}