JSFiddle - React, Tailwind, and code Playground

HTML

<body>
<p id="item">

</p>

</body>

JavaScript

var obj = {};
obj["Name"] = "Tom";
obj.lastName = "David";
obj["children"] = [];

var child1 = {name:"A", lastName:"Dav", age: 20};
var child2 = {name:"B", lastName:"Dav", age: 22};
var child3 = {name:"C", lastName:"D", age: 1};

obj["children"].push(child1);
obj["children"].push(child2);
child1["children"] = [];
child1["children"].push(child3);

var numberOfChildren = obj["children"].length;
var sumAge = sumAgeSuccessors(obj);

// Sum age of direct children
function sumAgeChildren(o){
  var sum = 0;
  for (var i=0; i<o["children"].length;i++){
   //  o["children"][i].age+=10;
     sum+=o["children"][i].age;
  }  
  return sum;
} 

// Sum age of successors
function sumAgeSuccessors(o){
  var sum = 0;
  for (var i=0; i<o["children"].length;i++){
    sum+=o["children"][i].age;
    if (o["children"][i]["children"])
      sum+=sumAgeSuccessors(o["children"][i]);
  }  
  return sum;
} 

var obj = {};
//obj["Name"] = 
var text = "sumAge = "+sumAge;
document.getElementById("item").innerHTML = text;