javascript document readyState

Returns the current download status of the document content. If a script (especially one initiated by a user event) can perform some actions while the document is still loading, but must avoid other actions until the entire page has loaded, this property provides intermediate information about the loading process. You would use its value in condition tests. The value of this property changes during loading as the loading state changes. Each change of the property value fires an onreadystatechange event.