There's no documentation for this item.
Source Code
# File action_view/helpers/prototype_helper.rb, line 1055 def build_callbacks(options) callbacks = {} options.each do |callback, code| if CALLBACKS.include?(callback) name = 'on' + callback.to_s.capitalize callbacks[name] = "function(request){#{code}}" end end callbacks end
<code/>and<pre/>for code samples.