Question

I have an object that I created previously.

obj = new Object();

I would like to fire a function each time this one of the object child is changed.

ex:

function changed()
{
  alert('Object changed';)
}

obj.test = 'blabla'; //fire changed().

Is this possible? Thank you

Answer 1

Yes and no. What you’re looking for are accessors and mutators (also known as getters and setters), but unfortunately they’re not cross-browser compatible.

If you just need to notice that the value has changed, and delays aren’t an issue, you could use a timeout loop for polling the value:

function check(key, context, callback)
{
  var cachedValue;
  cachedValue = context[key];
  function doCheck()
  {
    if ( cachedValue != context[key] ) callback();
    setTimeout(doCheck, 100);
  }
  doCheck();
}

check('test', obj, testChanged);

This is, of course, a very simple example of how a polling loop could work. There are better ways of doing this.