{
  const sleep = ms => {
    const d = $.Deferred()
    
    setTimeout(d.resolve, ms)
    
    return d.promise()
  }
  
  sleep(300).always(() => {
    console.log('失敗や成功にかかわらず実行される')
  })
}

{
  const sleep = ms => new Promise(resolve => setTimeout(resolve, ms))
  
  sleep(300).finally(() => {
    console.log('失敗や成功にかかわらず実行される')
  })
}