Question

I have to access property on object:

var jsonobj= {
    "first": {
        "second": 120
    }
}

How to check if second is available or not? jsonobj.hasOwnProperty() returns false if we check here.

If I want to change the value of second from 120 to 100, how can I achieve it?
Can I get a generalized solution, so that it works for any number of hierarchies?

Edit:
What if I don’t know the name of the property?

Answer 1

If you want to check the existence of [the unique path to] a nested property [key], this function may help:

function keyPathExists(obj,keypath){
  var keys = keypath.split('.'), key, trace = obj;
  while (key = keys.shift()){
    if (!trace[key]){
      return null
    };
    trace = trace[key];
  }
  return true;
}

//usages
var abcd = {a:{b:{c:{d:1}}}};
keyPathExists(abcd,'a.b.c.d'); //=> 1
keyPathExists(abcd,'a.b.c.d.e'); //=> null
if (keyPathExists(abcd,'a.b.c.d')){
 abcd.a.b.c.d = 2;
}

Please read @nnnnnns comment, especially the provided link within it carefully.