Object.defineProperty()

        var obj1 ={}
        Object.defineProperty(obj1,'txt',{
            get:function(){
                return obj1
            },
            set:function(newValue){
                document.getElementById('txt').value= newValue
                document.getElementById('show').innerHTML = newValue
            }
        })
        document.addEventListener('keyup',function(e){
            obj1.txt = e.target.value
        })