What does this jQuery line mean?

return $('<div>', {
       class: "开发者_StackOverflow中文版my_Class"
 });

It's returning a newly created <div class="my_Class"></div> element, this is the
$(html, props) overload of $(). It takes the element HTML and an object of properties to set.

Something to note though, class is a keyword in IE and will cause issues, you need to put it in quotes:

return $('<div>', { 'class': "my_Class" });

A more complete example may be something like:

return $('<div>', { 'class': "my_Class", click: function() { alert('hi'); } });

From the docs:

As of jQuery 1.4, we can pass a map of properties to the second argument. This argument accepts a superset of properties that can be passed to the .attr() method. Furthermore, any event type can be passed in, and the following jQuery methods can be called: val, css, html, text, data, width, height, or offset. Note that Internet Explorer will not allow you to create an input element and change its type; you must specify the type using <input type="checkbox" /> for example.