How can I use ruby on rails input field selector?

How can I use ruby on rails input field selector?

This is form:

<input id="user_user_name" class="form-control" type="text" name="user[user_name]" placeholder="Company Name">

Jquery

user_user_name:{       validators: {                                  notEmpty: {                             message: 'The company name is required and cannot be empty'          }     }   },