Simple form error display

form_errors.js.coffee

Backbone ||= {}

# This takes the place of the standard form / simple_form helpers in
# automatically displaying form errors when the errors have been sent back as
# json.
Backbone.form_errors = (selector, errors) ->
  $form = $(selector)

  clear_field = ($wrapper) ->
    $wrapper.removeClass('field_with_errors')
    $wrapper.find('span.error').remove()

  mark_field = ($wrapper, message) ->
    $wrapper.addClass('field_with_errors')
    $wrapper.append("<span class='error'>#{message}</span>")

  # Reset all errors
  clear_field($(field)) for field in $form.find('fieldset, div')

  # Mark any errors with names matching error keys
  for name, messages of errors
    $field   = $("[name*='[#{name}]']", $form)
    $wrapper = $field.parent()

    message = messages[0]

    mark_field($wrapper, message)