(function(){
    var root = this;
    function watch(obj, name, func){
        var value = obj[name];
 
        Object.defineProperty(obj, name, {
            get: function() {
                return value;
            },
            set: function(newValue) {
                value = newValue;
                func(value)
            }
        });
 
        if (value) obj[name] = value
    }
 
    this.watch = watch;
})();

var obj = {
    value: 1
}
 
watch(obj, "num", function(newvalue){
   
 var container = document.getElementById('container');
  console.log(contianer);
  document.getElementById('container').innerHTML = newvalue;
})
 
document.getElementById('button').addEventListener("click", function(){
    obj.value += 1;
});