问在Rails 4中正确实现Parsley.js自定义远程Validator

EN

<%=
    text_field_tag("access[username]",
                   value = nil,
                   options = {:"data-parsley-remote" => "" ,
                              :"data-parsley-remote-options" => "{ 'type': 'POST', 'dataType': 'json', 'data': { ':username': 'value' }}",
                              :"data-parsley-remote-validator" => "validate-username",
                              id:"username", placeholder:  t('access.simple_username'),
                              required: "required", pattern: "[a-z0-9_-]{3,64}$",
                              :"data-parsley-trigger" => "keyup",
                              :"data-parsley-minlength"=>"3" ,
                              :"data-parsley-maxlength"=>"64"})
%>

<script type="text/javascript">
    $('#username').bind('input propertychange', function()
    {
        window.Parsley.addAsyncValidator('validate-username', function (xhr) {
            // console.log(this.$element);
            // jQuery Object[ input[name="q"] ]
            var response = $.parseJSON(xhr.responseText);
            alert( JSON.stringify(response) );

            // Second Problem: How do I make data-parsley identify it is an error and mark the field red or something

        }, '/application/check_username_exists');
    }); </script>

  def check_username_exists
    username_exists = Access.exists?(username: params[:username])
    respond_to do |format|
      format.json { render json: {:"exists" => username_exists}.to_json }
      format.html
    end
  end