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

Source 

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