## Monitor variable changes <i>outside</i> of the GUI
Let's say you have a variable that changes by itself from time to time. If you'd like the GUI to reflect those changes, use the listen() method
GUI.add(obj, "propName").listen();
## Fire a function when someone uses a control
GUI.add(obj, "propName").onChange(function(n) {
alert("You changed me to " + n);
});
Initiated by [George Michael Brower]:http://georgemichaelbrower.com/ and [Jono Brandel]:http://jonobr1.com/ of the Data Arts Team, Google Creative Lab.