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};

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

var numberOfChildren = obj["children"].length;
var sumAge = sumAgeChildren(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;
} 


var text = "sumAge = "+sumAge;
document.getElementById("item").innerHTML = text;