# Managing object depths

# Determining an object's class (instanceof)

# Determining an object's type (typeof)

# Using the watch() method to set properties

You can use the `Object.watch` method to register a callback function to be invoked when a specified property of an ActionScript object changes. When the property changes, the callback function is invoked with `myObject` as the containing object. You must return the new value from the `object.watch` callback function; otherwise, the watched object property is assigned a value of `undefined`.

For example, in the code that follows, the `watch` method specifies a function to be invoked when the value for the `label` property of the CheckBox component is changed:

    function CheckBox() {
    	...
    	this.watch('label', function (id, oldval, newval){
    		...
    	});

    }

When the `label` property is modified, the specified function is invoked to perform any tasks needed to update the appearance and state of the component to reflect its new parameters. Therefore, the following assignment statement uses an `Object.watch` handler to notify the component that the variable has changed and causes it to update its graphical representation.

    myCheckBox1.value = false;

This syntax is more concise than using a method to update the `label` property:

    myCheckBox1.setLabel(false);

To remove a watchpoint, use the `Object.unwatch` method.

ActionScript DictionaryFor more information, see `Object.watch()` and the `Object object` entry.