JSFiddle - React, Tailwind, and code Playground

JavaScript

var x = { 
    a: 5, 
    b: "asdf" 
};
var y = { 
    a: 5, 
    b: "asdf" 
};

x.y = y;
y.x = x;

Object.prototype.clonage = function() {
  var newObj = (this instanceof Array) ? [] : {};
  for (i in this) {
    if (i == 'clone') continue;
    if (this[i] && typeof this[i] == "object") {
      newObj[i] = this[i].clonage();
    } else newObj[i] = this[i]
  } return newObj;
}
    
var z = x.clonage();
alert (z);