St. Louis Day of .NET – jQuery Plug-ins

This is part of a series of posts containing my notes from the sessions I attended at the 2011 St. Louis Day of .NET conference.

This series does not attempt to give complete accounts of the information presented in each session; it is just a way to capture the bullet points, notes, and opinions that I recorded while attending the conference. I have previously posted a list of all of the session materials and sample code that I have been able to find online, so if you are looking for a more precise account of a session, try looking there.

One of the better sessions I attended at this year’s conference was Ian Robinson’s “Building jQuery Plug-Ins”.  Too many sessions I attended this year skipped the how-to-get-started and jumped right into examining the code of a finished product.  This session, on the other hand, stepped through the entire process of building a jQuery plug-in.  Here are my notes from the session:

The Process

  • Wrap business logic with plug-in logic
  • The business logic can stay largely the same
  • Modify to inject settings and context
  • Modify for safety and to play well with others
    First step

Wrap in a closure…

(function($) {
     // ahh… safety

This structure ensures that our code doesn’t conflict with others (takes it out of global scope and defines the plug-in’s own scope).  It also ensures that when a dollar sign ($) is used in the body of this code, it means jQuery (and not anything else). (What’s A Closure?)

Define the Plug-in

No selecting needed:

     $.fn.myPlugin = function(options) {…};

Select and return (chain):

     $.fn.myPlugin = function(options) {
          return this.each(function() {

Establish Default Options

     $.fn.myPlugin.defaultOptions = {
          speed: ‘slow’

     var opts = $.extend({}, $.fn.myPlugin.defaultOptions, options);

Inject HTML Context

Options aren’t just for settings.

Inject all context through options.  For example:

          speed: ‘fast’,
          subNavSelector: ‘li.subnav’


Determine if you need to enforce document.ready.  If not, let the user of the plug-in do it.

If you’re ever unbinding events, bind with a namespace first.  For example:

     $(‘elem’).unbind(‘click.Namespace’, function(){…});

Complete Example

(function($) {
     $.fn.myPlugin = function(options) {
          var opts = $.extend({}, $.fn.myPlugin.defaultOptions, options), $moduleWrap = this;
          // Iterate over all elements contained in the current context ($moduleWrap = ".myClass"???)
          $moduleWrap.each(function() {
               // Grab the element being evaulated
               var $module = $(this);
               … do something …

     $.fn.myPlugin.defaultOptions = { 
          speed: ‘slow’ 
          subNavSelector: ‘li.subnav’

     $(document).ready(function() {

More examples and documentation (jQuery Crash Course)


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