How to use bootstrap-datepicker-rails with Bootstrap-Sass gem

_form.html.erb

<%= form_for(@person) do |f| %>
  <% if @person.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@person.errors.count, "error") %> prohibited this person from being saved:</h2>

      <ul>
      <% @person.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="row">
    <div class="field  span1">
      <%= f.label :name %><br />
      <%= f.text_field :name %>
    </div>
  <div class="field span2" data-behaviour='datepicker'>
      <%= f.label :dob %><br />
      <%= f.text_field :dob %>
    </div>
  </div>
  <div class="row">
    <div class="date_dob" id="date_dob">
      <%= hidden_field_tag( :_current_date, :value => today ) %>
    </div>    
    <div class="date_dob" id="date_dob_text">
      <%= text_field_tag( :_todays_date, :value => today ) %>
    </div>    

    <div class="field  span1" data-behaviour='datepicker'>
      <%= f.label :dod %><br />
      <%= f.text_field :dod %>
    </div>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

application.js

//= require jquery
//= require jquery_ujs
//= require bootstrap
//= require bootstrap-datepicker
//= require_tree .

var todaysDate = new Date();

$(document).on("focus", "[data-behaviour~='datepicker']", function(e){
    $(this).datepicker({"format": "yyyy-mm-dd", "weekStart": 1, "autoclose": true})
    $(this).datepicker().on('changeDate', function(ev) {
    	{alert ('Changed')};

    })
    // $(this).datepicker.on('changeDate', functin(ev) {
    // 	// if (ev.date.valueOf() > todaysDate.valueOf()) {
    // 	// 	$('#alert').show().find('strong').text('Date of Birth must not be after today!');
    // 	// } else {
    //  //        $('#alert').hide();
    //  //        startDate = new Date(ev.date);
    //  //        $('#date-start-display').text($('#date-start').data('date'));    		
    // 	// }
    //     // $('#date_dob').datepicker('hide');    	
    // }) ;
});

This datepicker is a jQuery plugin. It depends on jQuery. It doesn't extend the jQuery UI datepicker. It replaces it actually.

Date calculations are complicated stuff. Edge cases are common. That is why I said that you should do it in ruby. I have never done anything like that in javascript.

If you are doing this just for learning I will say 'fuck this feature' and move on. There is way too much to learn to waste so much time on a specific thing. When you are learning the first steps on something you want to get a overview of the whole thing as fast as possible.

The first book I read about Rails is Agile Web development with Rails. It is pretty good. Totally recommended :)

http://pragprog.com/book/rails4/agile-web-development-with-rails