1. DomName('NonElementParentNode.getElementById')
  2. DocsEditable()
  3. Experimental()
Element getElementById(String elementId)

Source 

@DomName('NonElementParentNode.getElementById')
@DocsEditable()
@Experimental() // untriaged
Element getElementById(String elementId) => _blink.BlinkNonElementParentNode.instance.getElementById_Callback_1_(this, elementId);