var result = element.readyState; element.readyState = value;
An object’s state is initially set to uninitialized, and then to loading. When data loading is complete, the state of the link object passes through the loaded and interactive states to reach the complete state. The states through which an object passes are determined by that object; an object can skip certain states (for example, interactive) if the state does not apply to that object. Data source objects and databound elements are normally populated asynchronously, and certain programmatic operations can only be performed reliably on databound objects when they are ready for use. Therefore, the appropriate code should be written to confirm the readyState of objects prior to performing certain operations on them. For example, walking the rows of a table should not be attempted until after the table has reached the complete state. The readyState property enables the status of an object to be tested. The correct place to test the readyState property is in the event handler for onreadystatechange. Similarly, a data source object (DSO) fires the ondatasetcomplete event to notify the document that the dataset is ready for programmatic operation.
Microsoft Developer Network: [Windows Internet Explorer API reference Article]