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'
         }
    }
  },