The Spider-Monkey JavaScript engine implements the noSuchMethod callback function for JavaScript Objects.

This function is called whenever JavaScript tries to execute an undefined method of an Object.

I would like to set a callback function to an Object that will be called whenever an undefined property in the Object is accessed or assigned to.

I haven't found a noSuchProperty function implemented for JavaScript Objects and I am curios if there is any workaround that will achieve the same result.

Consider the following code:

var a = {};
a.__defineGetter__("bla", function(){alert(1);return 2;});
alert(a.bla);

It is equivalent to [alert(1);alert(2)] - even though a.bla is undefined.

I would like to achieve the same result but to unknown properties (i.e. without knowing in advance that a."bla" will be the property accessed)