const SwapX = {

  observable : function observable(props){

    const _parent = this;

    let obj = {}, prop;

    const keys = Object.keys(props)

    for(let i=0; i < keys.length; i++){

       prop = keys[i];

       (function (prop){

         Object.defineProperty(obj,prop,{

          get: function(){

            return (this.value || props[prop] )

          },

          set: function(value){

            if(value !== this.value){

              this.value = value;

              _parent.markDirty(prop)

              _parent.run()

            }

          }

         })

       })(prop)

    }

    return obj

  },

  dirty : [],

  autorun : function (callback){

    this.run = callback;

  },

  markDirty(prop) {

    this.dirty.push(prop)

  }

}

​

const appState = SwapX.observable({

  count : 2,

  name : 'Swapnil'

})

​

SwapX.autorun(function(){

  console.log('Changed properties',SwapX.dirty)

})

​

var a = 1