How to use $.extend(); http://www.jquery4u.com/function-demos/extend/ Wrap it in jQuery Plugin : https://gist.github.com/ethyde/7060709

jquery-how-to-extend.js

// Use $.extend() to copy existing functionality
var demobox = $('#' + id);
demobox.empty();
 
var forms = {};
forms.enquiry = {
  email: 'enquiries@domain.com',
  sendForm: function () {
      //code which sends email
      demobox.append('sending email to: ' + this.email + '...' + '<br>');
  }
};
 
forms.contact = {
  email: 'contact@domain.com'
};
 
forms.feedback = {
  email: 'feedback@domain.com'
};
 
//Create a new object and copy the sendForm function from forms.enquiry to forms.contact and forms.feedback
forms.contact = $.extend({}, forms.enquiry, forms.contact);
forms.feedback = $.extend({}, forms.enquiry, forms.feedback);
 
forms.enquiry.sendForm();
forms.contact.sendForm();
forms.feedback.sendForm();
// Reset
$('#' + id).empty().hide();

// Result HTML
// sending email to: enquiries@domain.com...
// sending email to: contact@domain.com...
// sending email to: feedback@domain.com...


// Use $.extend() to specify custom settings for a plugin
$.fn.helloWorld = function (options) {
 
  // specify the default options for the plugin
  // Establish our default settings
  var settings = $.extend({
    text         : 'Hello, World!',
    color        : null,
    fontStyle    : null
  }, options);
  
  // Remember that within the plugin, this refers to the jQuery instance, and not the element, so we don’t need the wrapping $().
  // n'est pas forcément each(), mais une collection jQuery tel que bind()
  // http://remysharp.com/2010/06/03/signs-of-a-poorly-written-jquery-plugin/
  return this.each( function() {
    // ici $(this) est H2
    $(this).text( settings.text );

    if ( settings.color ) {
        $(this).css( 'color', settings.color );
    }

    if ( settings.fontStyle ) {
        $(this).css( 'font-style', settings.fontStyle );
    }
  });

};
 
$('h2').helloWorld({
  text        : 'Salut, le monde!',
  color       : '#005dff',
  fontStyle   : 'italic'
});

// With callback
$.fn.helloWorld = function (options) {
 
  // specify the default options for the plugin
  // Establish our default settings
  var settings = $.extend({
    text         : 'Hello, World!',
    color        : null,
    fontStyle    : null,
    complete     : null
  }, options);

  return this.each( function() {
    $(this).text( settings.text );

    if ( settings.color ) {
        $(this).css( 'color', settings.color );
    }

    if ( settings.fontStyle ) {
        $(this).css( 'font-style', settings.fontStyle );
    }
    
    // appele la function en callback s'il y en a une de définie
    if ( $.isFunction( settings.complete ) ) {
        settings.complete.call( this );
    }
  });
};

$('h2').helloWorld({
  text        : 'Salut, le monde!',
  color       : '#005dff',
  fontStyle   : 'italic',
  complete    : function() { alert( 'Done!' ) }
});