object.watch polyfill in ES5

object-watch.js

//Original code : https://gist.github.com/eligrey/384583
// modification 
//Objects like JSON can be observed using this
if (!Object.prototype.watch) {
    Object.defineProperty(
      Object.prototype,
      "watch", {
        enumerable: false,
        configurable: true,
        writable: false,
        value: function (prop, handler) {
          var old = this[prop];
           if(old){
                if(Object.keys(old).length>0){
                    var keys = Object.keys(old);
                    keys.forEach((ele)=>{
                        // console.log('inside',ele,this,this.ele); 
                        this[prop].watch(`${ele}`,handler);
                    })
                }
            }
        var cur = old;
        var getter = function () {
            return cur;
        };
        var setter = function (val) {
        old = cur;
        cur = handler.call(this,prop,old,val);
        return cur;
        };
        // can't watch constants
        if (delete this[prop]) {
            Object.defineProperty(this,prop,{
                get: getter,
                set: setter,
                enumerable: true,
                configurable: true
            });
        }
       }
    });
}