old_contents: import $ from 'jquery'
  import * as Fields from 'fields'
  
  $(document).on('keydown', Fields.SELECTOR, (e) => {
    Fields.setup($(e.target))
  })
  
new_contents: import $ from 'jquery'
  import * as Fields from 'fields'
  
  $(document).on('keypress focus', Fields.SELECTOR, (e) => {
    Fields.setup($(e.target))
  })
  
subject: initialize on keydown and focus