Provides a set of helpers for calling JavaScript functions and, most importantly, to call remote methods using what has been labelled AJAX. This means that you can call actions in your controllers without reloading the page, but still update certain parts of it using injections into the DOM. The common use case is having a form that adds a new element to a list without reloading the page.

To be able to use the JavaScript helpers, you must include the Prototype JavaScript Framework and for some functions script.aculo.us (which both come with Rails) on your pages. Choose one of these options:

  • Use <%= javascript_include_tag :defaults %> in the HEAD section of your page (recommended): The function will return references to the JavaScript files created by the rails command in your public/javascripts directory. Using it is recommended as the browser can then cache the libraries instead of fetching all the functions anew on every request.
  • Use <%= javascript_include_tag ‘prototype’ %>: As above, but will only include the Prototype core library, which means you are able to use all basic AJAX functionality. For the script.aculo.us-based JavaScript helpers, like visual effects, autocompletion, drag and drop and so on, you should use the method described above.
  • Use <%= define_javascript_functions %>: this will copy all the JavaScript support functions within a single script block.

For documentation on javascript_include_tag see ActionView::Helpers::AssetTagHelper.

If you’re the visual type, there’s an AJAX movie demonstrating the use of form_remote_tag.

Methods
Constants
CALLBACKS = [:uninitialized, :loading, :loaded, :interactive, :complete, :failure, :success].push((100..599).to_a).flatten
AJAX_OPTIONS = [ :before, :after, :condition, :url, :asynchronous, :method, :insertion, :position, :form, :with, :update, :script ].concat(CALLBACKS)
JAVASCRIPT_PATH = File.join(File.dirname(__FILE__), 'javascripts')
Public Instance methods
define_javascript_functions()

Includes the Action Pack JavaScript libraries inside a single <script> tag. The function first includes prototype.js and then its core extensions, (determined by filenames starting with "prototype"). Afterwards, any additional scripts will be included in random order.

Note: The recommended approach is to copy the contents of lib/action_view/helpers/javascripts/ into your application’s public/javascripts/ directory, and use javascript_include_tag to create remote <script> links.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 299
299:       def define_javascript_functions
300:         javascript = '<script type="text/javascript">'
301:         
302:         # load prototype.js and its extensions first 
303:         prototype_libs = Dir.glob(File.join(JAVASCRIPT_PATH, 'prototype*')).sort.reverse
304:         prototype_libs.each do |filename| 
305:           javascript << "\n" << IO.read(filename)
306:         end
307:         
308:         # load other librairies
309:         (Dir.glob(File.join(JAVASCRIPT_PATH, '*')) - prototype_libs).each do |filename| 
310:           javascript << "\n" << IO.read(filename)
311:         end
312:         javascript << '</script>'
313:       end
draggable_element(element_id, options = {})

Makes the element with the DOM ID specified by element_id draggable.

This method requires the inclusion of the script.aculo.us JavaScript library.

Example:

  <%= draggable_element("my_image", :revert => true)

You can change the behaviour with various options, see script.aculo.us for more documentation.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 424
424:       def draggable_element(element_id, options = {})
425:         javascript_tag("new Draggable('#{element_id}', #{options_for_javascript(options)})")
426:       end
drop_receiving_element(element_id, options = {})

Makes the element with the DOM ID specified by element_id receive dropped draggable elements (created by draggable_element). and make an AJAX call By default, the action called gets the DOM ID of the element as parameter.

This method requires the inclusion of the script.aculo.us JavaScript library.

Example:

  <%= drop_receiving_element("my_cart", :url => { :controller => "cart", :action => "add" }) %>

You can change the behaviour with various options, see script.aculo.us for more documentation.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 440
440:       def drop_receiving_element(element_id, options = {})
441:         options[:with]     ||= "'id=' + encodeURIComponent(element.id)"
442:         options[:onDrop]   ||= "function(element){" + remote_function(options) + "}"
443:         options.delete_if { |key, value| AJAX_OPTIONS.include?(key) }
444:         
445:         options[:accept] = array_or_string_for_javascript(options[:accept]) if options[:accept]    
446:         options[:hoverclass] = "'#{options[:hoverclass]}'" if options[:hoverclass]
447:         
448:         javascript_tag("Droppables.add('#{element_id}', #{options_for_javascript(options)})")
449:       end
escape_javascript(javascript)

Escape carrier returns and single and double quotes for JavaScript segments.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 452
452:       def escape_javascript(javascript)
453:         (javascript || '').gsub(/\r\n|\n|\r/, "\\n").gsub(/["']/) { |m| "\\#{m}" }
454:       end
evaluate_remote_response()

Returns ‘eval(request.responseText)’ which is the Javascript function that form_remote_tag can call in :complete to evaluate a multiple update return document using update_element_function calls.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 250
250:       def evaluate_remote_response
251:         "eval(request.responseText)"
252:       end
form_remote_tag(options = {})

Returns a form tag that will submit using XMLHttpRequest in the background instead of the regular reloading POST arrangement. Even though it’s using JavaScript to serialize the form elements, the form submission will work just like a regular submission as viewed by the receiving side (all elements available in @params). The options for specifying the target with :url and defining callbacks is the same as link_to_remote.

A "fall-through" target for browsers that doesn’t do JavaScript can be specified with the :action/:method options on :html

  form_remote_tag :html => { :action => url_for(:controller => "some", :action => "place") }

The Hash passed to the :html key is equivalent to the options (2nd) argument in the FormTagHelper.form_tag method.

By default the fall-through action is the same as the one specified in the :url (and the default method is :post).

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 158
158:       def form_remote_tag(options = {})
159:         options[:form] = true
160: 
161:         options[:html] ||= {}
162:         options[:html][:onsubmit] = "#{remote_function(options)}; return false;"
163:         options[:html][:action] = options[:html][:action] || url_for(options[:url])
164:         options[:html][:method] = options[:html][:method] || "post"
165: 
166:         tag("form", options[:html], true)
167:       end
javascript_tag(content)

Returns a JavaScript tag with the content inside. Example:

  javascript_tag "alert('All is good')" # => <script type="text/javascript">alert('All is good')</script>
     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 458
458:       def javascript_tag(content)
459:         content_tag("script", javascript_cdata_section(content), :type => "text/javascript")
460:       end
link_to_function(name, function, html_options = {})

Returns a link that’ll trigger a javascript function using the onclick handler and return false after the fact.

Examples:

  link_to_function "Greeting", "alert('Hello world!')"
  link_to_function(image_tag("delete"), "if confirm('Really?'){ do_delete(); }")
    # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 42
42:       def link_to_function(name, function, html_options = {})
43:         content_tag(
44:           "a", name, 
45:           {:href => "#", :onclick => "#{function}; return false;"}.merge(html_options.symbolize_keys)
46:         )
47:       end
link_to_remote(name, options = {}, html_options = {})

Returns a link to a remote action defined by options[:url] (using the url_for format) that’s called in the background using XMLHttpRequest. The result of that request can then be inserted into a DOM object whose id can be specified with options[:update]. Usually, the result would be a partial prepared by the controller with either render_partial or render_partial_collection.

Examples:

 link_to_remote "Delete this post", :update => "posts", :url => { :action => "destroy", :id => post.id }
 link_to_remote(image_tag("refresh"), :update => "emails", :url => { :action => "list_emails" })

You can also specify a hash for options[:update] to allow for easy redirection of output to an other DOM element if a server-side error occurs:

Example:

 link_to_remote "Delete this post",
     :url => { :action => "destroy", :id => post.id },
     :update => { :success => "posts", :failure => "error" }

Optionally, you can use the options[:position] parameter to influence how the target DOM element is updated. It must be one of :before, :top, :bottom, or :after.

By default, these remote requests are processed asynchronous during which various JavaScript callbacks can be triggered (for progress indicators and the likes). All callbacks get access to the request object, which holds the underlying XMLHttpRequest.

To access the server response, use request.responseText, to find out the HTTP status, use request.status.

Example:

  link_to_remote word,
      :url => { :action => "undo", :n => word_counter },
      :complete => "undoRequestCompleted(request)"

The callbacks that may be specified are (in order):

:loading:Called when the remote document is being loaded with data by the browser.
:loaded:Called when the browser has finished loading the remote document.
:interactive:Called when the user can interact with the remote document, even though it has not finished loading.
:success:Called when the XMLHttpRequest is completed, and the HTTP status code is in the 2XX range.
:failure:Called when the XMLHttpRequest is completed, and the HTTP status code is not in the 2XX range.
:complete:Called when the XMLHttpRequest is complete (fires after success/failure if they are present).,

You can further refine :success and :failure by adding additional callbacks for specific status codes:

Example:

  link_to_remote word,
      :url => { :action => "action" },
      404 => "alert('Not found...? Wrong URL...?')",
      :failure => "alert('HTTP Error ' + request.status + '!')"

A status code callback overrides the success/failure handlers if present.

If you for some reason or another need synchronous processing (that’ll block the browser while the request is happening), you can specify options[:type] = :synchronous.

You can customize further browser side call logic by passing in JavaScript code snippets via some optional parameters. In their order of use these are:

:confirm:Adds confirmation dialog.
:condition:Perform remote request conditionally by this expression. Use this to describe browser-side conditions when request should not be initiated.
:before:Called before request is initiated.
:after:Called immediately after request was initiated and before :loading.
:submit:Specifies the DOM element ID that’s used as the parent of the form elements. By default this is the current form, but it could just as well be the ID of a table row or any other DOM element.
     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 134
134:       def link_to_remote(name, options = {}, html_options = {})  
135:         link_to_function(name, remote_function(options), html_options)
136:       end
observe_field(field_id, options = {})

Observes the field with the DOM ID specified by field_id and makes an AJAX call when its contents have changed.

Required options are:

:url:url_for-style options for the action to call when the field has changed.

Additional options are:

:frequency:The frequency (in seconds) at which changes to this field will be detected. Not setting this option at all or to a value equal to or less than zero will use event based observation instead of time based observation.
:update:Specifies the DOM ID of the element whose innerHTML should be updated with the XMLHttpRequest response text.
:with:A JavaScript expression specifying the parameters for the XMLHttpRequest. This defaults to ‘value’, which in the evaluated context refers to the new field value.

Additionally, you may specify any of the options documented in link_to_remote.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 338
338:       def observe_field(field_id, options = {})
339:         if options[:frequency] and options[:frequency] > 0
340:           build_observer('Form.Element.Observer', field_id, options)
341:         else
342:           build_observer('Form.Element.EventObserver', field_id, options)
343:         end
344:       end
observe_form(form_id, options = {})

Like observe_field, but operates on an entire form identified by the DOM ID form_id. options are the same as observe_field, except the default value of the :with option evaluates to the serialized (request string) value of the form.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 350
350:       def observe_form(form_id, options = {})
351:         if options[:frequency]
352:           build_observer('Form.Observer', form_id, options)
353:         else
354:           build_observer('Form.EventObserver', form_id, options)
355:         end
356:       end
periodically_call_remote(options = {})

Periodically calls the specified url (options[:url]) every options[:frequency] seconds (default is 10). Usually used to update a specified div (options[:update]) with the results of the remote call. The options for specifying the target with :url and defining callbacks is the same as link_to_remote.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 141
141:       def periodically_call_remote(options = {})
142:          frequency = options[:frequency] || 10 # every ten seconds by default
143:          code = "new PeriodicalExecuter(function() {#{remote_function(options)}}, #{frequency})"
144:          javascript_tag(code)
145:       end
remote_function(options)

Returns the javascript needed for a remote function. Takes the same arguments as link_to_remote.

Example:

  <select id="options" onchange="<%= remote_function(:update => "options", :url => { :action => :update_options }) %>">
    <option value="0">Hello</option>
    <option value="1">World</option>
  </select>
     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 262
262:       def remote_function(options)
263:         javascript_options = options_for_ajax(options)
264: 
265:         update = ''
266:         if options[:update] and options[:update].is_a?Hash
267:           update  = []
268:           update << "success:'#{options[:update][:success]}'" if options[:update][:success]
269:           update << "failure:'#{options[:update][:failure]}'" if options[:update][:failure]
270:           update  = '{' + update.join(',') + '}'
271:         elsif options[:update]
272:           update << "'#{options[:update]}'"
273:         end
274: 
275:         function = update.empty? ? 
276:           "new Ajax.Request(" :
277:           "new Ajax.Updater(#{update}, "
278: 
279:         function << "'#{url_for(options[:url])}'"
280:         function << ", #{javascript_options})"
281: 
282:         function = "#{options[:before]}; #{function}" if options[:before]
283:         function = "#{function}; #{options[:after]}"  if options[:after]
284:         function = "if (#{options[:condition]}) { #{function}; }" if options[:condition]
285:         function = "if (confirm('#{escape_javascript(options[:confirm])}')) { #{function}; }" if options[:confirm]
286: 
287:         return function
288:       end
sortable_element(element_id, options = {})

Makes the element with the DOM ID specified by element_id sortable by drag-and-drop and make an AJAX call whenever the sort order has changed. By default, the action called gets the serialized sortable element as parameters.

This method requires the inclusion of the script.aculo.us JavaScript library.

Example:

  <%= sortable_element("my_list", :url => { :action => "order" }) %>

In the example, the action gets a "my_list" array parameter containing the values of the ids of elements the sortable consists of, in the current order.

You can change the behaviour with various options, see script.aculo.us for more documentation.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 400
400:       def sortable_element(element_id, options = {})
401:         options[:with]     ||= "Sortable.serialize('#{element_id}')"
402:         options[:onUpdate] ||= "function(){" + remote_function(options) + "}"
403:         options.delete_if { |key, value| AJAX_OPTIONS.include?(key) }
404:         
405:         [:tag, :overlap, :constraint, :handle].each do |option|
406:           options[option] = "'#{options[option]}'" if options[option]
407:         end
408:         
409:         options[:containment] = array_or_string_for_javascript(options[:containment]) if options[:containment]
410:         options[:only] = array_or_string_for_javascript(options[:only]) if options[:only]
411:         
412:         javascript_tag("Sortable.create('#{element_id}', #{options_for_javascript(options)})")
413:       end
submit_to_remote(name, value, options = {})

Returns a button input tag that will submit form using XMLHttpRequest in the background instead of regular reloading POST arrangement. options argument is the same as in form_remote_tag

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 171
171:       def submit_to_remote(name, value, options = {})
172:         options[:with] ||= 'Form.serialize(this.form)'
173: 
174:         options[:html] ||= {}
175:         options[:html][:type] = 'button'
176:         options[:html][:onclick] = "#{remote_function(options)}; return false;"
177:         options[:html][:name] = name
178:         options[:html][:value] = value
179: 
180:         tag("input", options[:html], false)
181:       end
update_element_function(element_id, options = {}, &block)

Returns a Javascript function (or expression) that’ll update a DOM element according to the options passed.

  • :content: The content to use for updating. Can be left out if using block, see example.
  • :action: Valid options are :update (assumed by default), :empty, :remove
  • :position If the :action is :update, you can optionally specify one of the following positions: :before, :top, :bottom, :after.

Examples:

  <%= javascript_tag(update_element_function(
        "products", :position => :bottom, :content => "<p>New product!</p>")) %>

  <% replacement_function = update_element_function("products") do %>
    <p>Product 1</p>
    <p>Product 2</p>
  <% end %>
  <%= javascript_tag(replacement_function) %>

This method can also be used in combination with remote method call where the result is evaluated afterwards to cause multiple updates on a page. Example:

  # Calling view
  <%= form_remote_tag :url => { :action => "buy" }, :complete => evaluate_remote_response %>
  all the inputs here...

  # Controller action
  def buy
    @product = Product.find(1)
  end

  # Returning view
  <%= update_element_function(
        "cart", :action => :update, :position => :bottom,
        :content => "<p>New Product: #{@product.name}</p>")) %>
  <% update_element_function("status", :binding => binding) do %>
    You've bought a new product!
  <% end %>

Notice how the second call doesn’t need to be in an ERb output block since it uses a block and passes in the binding to render directly. This trick will however only work in ERb (not Builder or other template forms).

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 221
221:       def update_element_function(element_id, options = {}, &block)
222:         
223:         content = escape_javascript(options[:content] || '')
224:         content = escape_javascript(capture(&block)) if block
225:         
226:         javascript_function = case (options[:action] || :update)
227:           when :update
228:             if options[:position]
229:               "new Insertion.#{options[:position].to_s.camelize}('#{element_id}','#{content}')"
230:             else
231:               "$('#{element_id}').innerHTML = '#{content}'"
232:             end
233:           
234:           when :empty
235:             "$('#{element_id}').innerHTML = ''"
236:           
237:           when :remove
238:             "Element.remove('#{element_id}')"
239:           
240:           else
241:             raise ArgumentError, "Invalid action, choose one of :update, :remove, :empty"
242:         end
243:         
244:         javascript_function << ";\n"
245:         options[:binding] ? concat(javascript_function, options[:binding]) : javascript_function
246:       end
visual_effect(name, element_id = false, js_options = {})

Returns a JavaScript snippet to be used on the AJAX callbacks for starting visual effects.

This method requires the inclusion of the script.aculo.us JavaScript library.

Example:

  <%= link_to_remote "Reload", :update => "posts",
        :url => { :action => "reload" },
        :complete => visual_effect(:highlight, "posts", :duration => 0.5 )

If no element_id is given, it assumes "element" which should be a local variable in the generated JavaScript execution context. This can be used for example with drop_receiving_element:

  <%= drop_receving_element (...), :loading => visual_effect(:fade) %>

This would fade the element that was dropped on the drop receiving element.

You can change the behaviour with various options, see script.aculo.us for more documentation.

     # File vendor/rails/actionpack/lib/action_view/helpers/javascript_helper.rb, line 378
378:       def visual_effect(name, element_id = false, js_options = {})
379:         element = element_id ? "'#{element_id}'" : "element"
380:         js_options[:queue] = "'#{js_options[:queue]}'" if js_options[:queue]
381:         "new Effect.#{name.to_s.camelize}(#{element},#{options_for_javascript(js_options)});"
382:       end