Indicates if there is a previous page of data.
Returns true if the current page is not the first
page in the dataset.
Returns false if the current page is the first
page in the dataset.
Calling hasPreviousPage() on a write-only dataset causes an error.
Note:
A dataset needs to load its data before you call its hasPreviousPage() function.
Usually a dataset finishes loading a short time after the page it is on finishes
loading. So if you call hasPreviousPage() inside the page’s onReady()
event handler, the dataset might not be ready yet.
To call hasPreviousPage() as soon as possible after a page loads, use the dataset's
onReady() function inside the page’s onReady()
event handler to ensure that both the page and the dataset have finished loading.