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Watches for a property to be assigned a value and runs a function when that occurs.
Method of Object
Syntax
watch( prop, handler )
Parameters
| Parameter | Description |
|---|---|
| prop | The name of a property of the object. |
| handler | A function to call. |
Description
Watches for assignment to a property named prop in this object, calling handler(prop, oldval, newval) whenever prop is set and storing the return value in that property. A watchpoint can filter (or nullify) the value assignment, by returning a modified newval (or oldval).
If you delete a property for which a watchpoint has been set, that watchpoint does not disappear. If you later recreate the property, the watchpoint is still in effect.
To remove a watchpoint, use the Object.unwatch method. By default, the watch method is inherited by every object descended from Object.