Unobtrusive Javascript helper for dynamically creating fields_for objects for Rails.

Minimum Requirements

  • JQuery 1.7 or higher
  • Rails 2.3.2 to 3.*


  1. Download numerous.js file
  2. Move it to your javascript folder or anywhere that can be accessed by your app
  3. Include it in your html file

Live Demo

Try Numerous.js!!

Quick Start

  1. Create an element where the new forms will be appended.

    <div id="list"></div>
  2. Create a fields_for template to be used when adding a new object.

    <div id="fields-for-list" class="numerous'>
      <%= form.fields_for :objects,, :child_index => 'replace_this' do |f| %>
        <%= f.text_field :object_field %>
        <%= f.text_field :another_object_field %>
        <%= link_to 'Remove', '#', :class => 'numerous-remove' %>
  3. Create a link for adding new objects.

    <%= link_to 'Add Object', '#', :id => 'add-to-list' %>
  4. Call Numerous.init() when the document is ready:


Naming Conventions

  1. The whole fields_for section must be under a div like this:

    <div id="fields-for-[list id]" class="numerous">
  2. fields_for objects must have 'replace_this' as the :child_index value.

    <%= form.fields_for :objects,, :child_index => 'replace_this' do |f| %>
  3. Put a numerous-remove link if you want the ability to delete objects.

    <%= link_to 'Remove', '#', :class => 'numerous-remove' %>

Set :allow_destroy => true to the parent model if you want this functionality.

    class Parent < ActiveRecord::Base
      has_many :lists
      accepts_nested_attributes_for :lists, :allow_destroy => true
  1. The add link must follow this id template:

    <%= link_to 'Add Object', '#', :id => 'add-to-[list id]' %>


You can add callbacks which will be called after adding or removing a fields_for instance.

      'list-name' : {
        'add' : function(form){
          alert("I'm adding another fields_for instance!");
          // do something here

        'remove' : function(form){
          alert("I'm removing a fields_for instance!");
          // do something here

The add and remove callbacks take 1 parameter which is the fields_for element that is added or removed.

Updating Objects

By default numerous.js is adding fields-for-[list id] class to all fields_for instance you've added. If you want to be able to remove existing objects, put the fields_for under a fields-for-[list id] div.

    <% parent.lists.each do |list| %>
      <div class='fields-for-list'>
        <%= form.fields_for :list, list do |f| %>
          <%= f.text_field :object_field %>
          <%= f.text_field :another_object_field %>
          <%= link_to 'Remove', '#', :class => 'numerous-remove' %>
        <% end %>
    <% end %>

Initialization Options

add : function() - A callback that will be called every time a new object is added.

remove : function() - A callback that will be called every time an object is removed.

initial : number | function() - An integer or a funtion that returns an integer. - The list will initially have this number of object. - defaults to 0.

after-initialize : function() - A callback that will be called after initializing the list.

Helper Methods

Numerous.count(String list) - returns the current count (Number) of the visible objects under the passed list

Numerous.get(String list) - returns all the objects (HTML Elements) under the passed list

Numerous.removeAll(String list) - triggers the remove link of all the list objects


Karl Bryan P. Paragua


numerous.js is a free software, and may be redistributed under the terms specified in the LICENSE file.