JSFiddle - React, Tailwind, and code Playground

JavaScript

var obj = {
  emptyValue: null,
  get: function(prop){
    if(typeof this[prop] == "undefined")
        return this.emptyValue;
    else
        return this[prop];
  },
  set: function(prop,value){
    this[prop] = value;
  }
};

alert('Empty value: ' + obj.get('not set value'));

obj.set('set value','VALUE');
alert('Previously set value: ' + obj.get('set value'));