amcharts5 use series.getDataItemById() find child return undefined

Question

  document.querySelector('button').addEventListener('click',_ => {
    let itm1 = series.getDataItemById('Root');// return DataItem

    let itm2 = series.getDataItemById('A0');// undefined
    series.set("selectedDataItem",itm2); // and not work
  });

CodePen

Ive tried multiple variations of this, but none of them seem to work. Any ideas? Thanks in advance.

Answer 1

After looking at the source code, can use get ('children ') to obtain child nodes

let item = series.getDataItemById('Root');
series.set("selectedDataItem",item.get('children')[0]);