1. @DomName('CharacterData.substringData')
  2. @DocsEditable()
String substringData(int offset, int count)

Source 

@DomName('CharacterData.substringData')
@DocsEditable()
String substringData(int offset, int count) =>
    _blink.BlinkCharacterData.instance
        .substringData_Callback_2_(this, offset, count);