How to Monitor the Setting of new Properties on Javascript Objects -

how callback whenever new properties set on javascript object..?
i.e. don't know properties going set, want callback properties that set.

what want is

var obj = {}; obj.a = "something"; // triggers callback function  function callback(obj,key,val) {     console.log(key + " set " + val + " on ", obj); } 

is possible?

you can use new defineproperty:

function onchange(propertyname, newvalue){ ... }  var o = {};  object.defineproperty(o, "propertyname", {   get: function() {return pvalue; },  set: function(newvalue) { onchange("propertyname",newvalue); pvalue = newvalue;}}); 

but depends on browser version need support.

edit: added snippet on jsfiddle, works in ie10. http://jsfiddle.net/r2wbr/