[shared] range overlap check

overlap = !((end2 < start1) || (start2 > end1))

r = Range.find_all(:conditions => ["NOT ((end < ?) || (start > ?))", new_start, new_end])

overlap = r.present?
number_of_overlaps = r.length

dynamic form with accept_nested_attributes

http://railsforum.com/viewtopic.php?id=28447

jQuery ExtendedHelper

http://code.google.com/p/jquery-extendedhelper/

jQuery hash merge

merge hash2 to hash1:

$.extend(hash1, hash2);

for recursive merge:

$.extend(true, hash1, hash2);

add javascript files to rails default

environment.rb

# reset:
ActionView::Helpers::AssetTagHelper::JAVASCRIPT_DEFAULT_SOURCES = [
  'jquery-1.4.3', 'jquery-ui-1.8.6.custom', 'jrails',
  'jquery.extended_helper_2.0', 'date-id', 'jquery.gritter'
]
ActionView::Helpers::AssetTagHelper::reset_javascript_include_default

# adding:
ActionView::Helpers::AssetTagHelper::register_javascript_include_default 'extended_helper', 'date'