document.documentElement.focus()

focus.md

http://crbug.com/467043

IE11:
  (default)
  document.body.tabIndex = 0
  document.head.tabIndex = 0
  document.documentElement.tabIndex = 0
  
  document.body.focus() -> work (regardless of tabIndex)
  document.documentElement.focus() -> work (regardless of tabIndex)
  document.head.focus() -> doesn't work (regardless of tabIndex)

Chrome44:
  (default)
  document.body.tabIndex = -1
  document.head.tabIndex = -1
  document.documentElement.tabIndex = -1

  document.body.focus() -> work (when tabindex != -1)
  document.documentElement.focus() -> work (tabindex != -1)
  document.head.focus() -> doesn't work (regardless of tabIndex)

Firefox39:
  (default)
  document.body.tabIndex = -1
  document.head.tabIndex = -1
  document.documentElement.tabIndex = -1

  document.body.focus() -> work (when tabIndex != -1)
  document.documentElement.focus() -> work (regardless of tabIndex)
  document.head.focus() -> doesn't work (regardless of tabIndex)

Noiceeeee🎈