[рони]

Epitough,

<script>
const graph = {
  value: 65, children: [{
    value: 15,
    children: [{
      value: 55,
      children: [{
        value: 85,
        children: [{
          value: 66,
          children: [{ value: 29 }, { value: 21 }]
        }]
      }]
    }]
  }]
};
let example = foo(graph);

function foo(elem) {
    let obj = {
        max: elem.value,
        min: elem.value
    };
    if (elem.children) {
        elem.children.map(foo).forEach(
            function(o) {
                obj.max = Math.max(obj.max, o.max);
                obj.min = Math.min(obj.min, o.min);
            }

        );

    }
    return obj;
}

document.write(JSON.stringify(example))


  </script>