vitaliyserebryanskiy

const sum = data =>
  (data instanceof Array ? data : [ data ]).reduce((acc, n) => {
    return acc + n.value + sum(n.children || []);
  }, 0);


const valueSum = sum(valueList);

function sum(data) {
  let result = 0;

  for (const stack = [].concat(data); stack.length;) {
    const { value, children: c } = stack.pop();
    stack.push(...(Array.isArray(c) ? c : []));
    result += value;
  }

  return result;
}