Drupal 7 Module Development

Chapter 10
Once the response is set up it is inserted into a renderable array. The type is
ajax_commands, which will know how to render the AJAX command that was created
in the callback. To send the AJAX response properly ajax_deliver() is used. This
function properly formats the response for the JavaScript on the receiving side.
Additionally, Drupal tracks the JavaScript and CSS files within a page. If a new
file is added within an AJAX request that is not already loaded in the page the new
file is sent as part of the response and added to the page along with the rest of
the response.
For cases when JavaScript is not available in the initial page view and the link is
followed, it is treated as a full page request and the user is sent to a new page. This
page lives at the same callback that built the AJAX response. The difference is nojs is
passed into the callback so it knows the response is not in AJAX. In this case the else
is executed generating a different message for the new page.
AJAX commands
Drupal provides several AJAX commands that can add or alter content in a page
using jQuery methods. In the previous section we covered ajax_command_append().
Here are all the possible commands that can be used.
ajax_command_after
When ajax_command_after() is used, jQuery.after() is the method used to
add content to the page. The arguments are $selector, $content, and $settings.
$selector is the jQuery selector on the page and $content is the content to add
after the selector. $settings, the third argument, is a set of settings used by the
behaviors for this single command.
ajax_command_alert
The alert command is a core JavaScript command. ajax_command_alert($text) is
used to alert returned text. The text is presented in an alert box.
ajax_command_append
This command is similar to ajax_command_after. Instead of adding the content
after the selector it appends it to the end of the selector. The interface to the function
is the same as ajax_command_after() with the $selector, $content, and
$settings arguments. $selector is the jQuery selector on the page, $content is
the content to append to the selector, and $settings is used by behavior for just
this one command.
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