Question

In the following jQuery, the .each() method takes two arguments: 'ul li a' and menu. What do these two arguments mean?

var menu = $('.menu');
$('ul li a', menu).each(function() {
    $(this).append('<span />');
});

HTML:

<div class="menu">
    <ul>
        <li><a href="#">Edit Profile</a></li>
        <li><a href="#">Account Settings</a></li>
        <li><a href="#">Appear Offline</a></li>
        <li><a href="#">Logout</a></li>
    </ul>
</div>

Answer 1

The second parameter to the jQuery function is the context. This tells jQuery to only search for elements that are in that context

So for your example:

$('ul li a', menu).each(function() {
    $(this).append('<span />');
});

This will only search for anchors within li’s within a ul, that are also located inside of menu.

This can be a very useful optimization since it can significantly cut down the amount of space jQuery has to search.

EDIT

To possibly make this a bit clearer (as jfriend00 points out), your particular example, $('ul li a', menu), is equivalent to $('.menu ul li a')

The context parameter is explained here in the docs