PDFView.open() is done?

Using PDFView.open(), how do i know when pdf or first page is loaded?

[MickL]

Is this new? I get Cannot read property 'then' of undefined Im using version 1.1.1

PDFViewerApplication.open('myURL').then(function() {
           console.log('DONE');
})

P.S. Thanks alot for your blazing fast answer(s)!

[yurydelendik]

It is there since v1.2.109 (Nov, 2015) and now currently 1.3 released and 1.4 in beta.