Add X-CSRF-Token header for ajax call to pass csrf verfication

gistfile1.js

// reference : http://stackoverflow.com/questions/7203304/warning-cant-verify-csrf-token-authenticity-rails
//            : http://stackoverflow.com/questions/8511695/rails-render-json-session-lost 
  
$.ajax({ url: 'YOUR URL HERE',
  type: 'POST',
  beforeSend: function(xhr) {
    xhr.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content'))
  },
  data: 'someData=' + someData,
  success: function(response) {
    $('#someDiv').html(response);
  }
});


$.ajax({
  type: 'post',
  data: $(this).sortable('serialize'),
  headers: {
    'X-CSRF-Token': '<%= form_authenticity_token.to_s %>'
  },
  complete: function(request){},
  url: "<%= sort_widget_images_path(@widget) %>"
})

$(document).ajaxSend(function(e, xhr, options) {
  var sid = $("meta[name='csrf-token']").attr("content");
  xhr.setRequestHeader("X-CSRF-Token", sid);
});