IsPostBack for Client-Side Code

In client-side code, I needed to determine whether the pageLoad function was being run the first time the page was loaded or on a subsequent postback. Searching around, many said there was no such function. But then I came across one posting which illustrated that there indeed is ... at least to detect partial postbacks:

function pageLoad(sender, e)
{
if (!e.get_isPartialLoad())
{

}
}