How to understand if (close === false) ?

[zhishaofei3]

handleCallback_: function () {
    var success = document.createElement('div')
    success.classList.add('overlay')
    success.setAttribute('role', 'alert')
    success.textContent = 'Data has been cleared.'
    document.body.appendChild(success)

    setTimeout(function () {
      success.classList.add('visible')
    }, 10)
    setTimeout(function () {
      if (close === false) // how to understand this line ? what is close ?
        success.classList.remove('visible')
      else
        window.close()
    }, 4000)
  },

how to understand this line ? what is close ?