Drupal behaviors

Question

• What are Drupal behaviors at all?
• What type of service layer it offers to module developers?
• What type of relation it maps to jQuery.ready?

Answer 1

Long version: Drupal.behaviors is not simply a replacement for jQuery.ready since the latter only runs once (when DOM is ready for manipulation): behaviors can be fired multiple times during page execution and can be run whenever new DOM elements are inserted into the document.

Also, modules could override or extend an existing behavior (e.g. if one module has a behavior of adding a bounce effect on all links, a second module could replace the behavior by a different bounce effect).

Short version: it's more modular, though the documentation could be improved.

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Also, starting in Drupal 7, settings defined using drupal_add_js (PHP) or in Drupal.settings.modulename (Javascript) are directly passed as second parameter (the first one being the context) to the behavior.

For example:

Drupal.behaviors.changeLinks = function(context, settings){     if (!settings) settings = Drupal.settings.changeLinks;     $("a", context).hover(function() {         $(this).css('color', settings.color);     }); }; 

And if one of your script (or another) creates new nodes, it could still have the behaviors applied to the new nodes without having to know what other modules are iinstalled:

var newNodes = $('<a href="#">Hello</a> <a href="#">World</a>').appendTo('#someDiv');  Drupal.attachBehaviors(newNodes); 

Answer 2

Duplicated Functionality

Note that the Drupal.behaviors architecture duplicates functionality already in jQuery.

Also, as of this writing, there does not appear to be any documentation or case studies for Drupal.behaviors outside of Drupal itself; and the documentation within Drupal (as stated above) could benefit considerably from improvements. As of this writing, it appears that the primary detailed documentation is restricted-access for-fee only.

This means you may notice performance degredation, anomalies, and unexpected results not consistent with standard jQuery that are endemic to the Drupal.behaviors ecosystem.

Native jQuery Functionality

In contrast to Drupal.behaviors, the built-in functionality of the standard jQuery API is extensively documented including in-line demonstrations and examples. Moreover, there are numerous live examples freely available on sites such as jsfiddle.

The links in the see also section enumerate the jQuery api calls relevant to handling new DOM elements inserted into the document.

See also

• http://api.jquery.com/on/
• http://api.jquery.com/live/
• http://api.jquery.com/bind/
• http://api.jquery.com/delegate/