x= {foo:"bar",
    esta: "es"};


class Robj {
 constructor(o) {
   Object.assign(this, o);
 }

 map(fn) {
   return Object.keys(this)
                .reduce((obj, key) => Object.assign(obj, {[key]: fn(key, this[key], this)}),
                        {});
 }
 filter(fn) {
   return Object.keys(this)
                .filter( key => {
                  const result = fn(key, this[key], this);
                  return result === false || result === null;
                })
                .reduce((obj, key) => Object.assign(obj, {[key]: fn(key, this[key], this)}),
                        {});
 }
}
var y = new Robj(x);

z= y.map((key, value) => key + "ASD");

console.log(z)