The almost-22-year-old singer had early celebrations this weekend
It's currently unknown whether the song was a leftover from his hit 'Purpose' LP
Sia, David Guetta, Faithless, Kaiser Chiefs, Bastille and Little Mix will also perform
Also featuring Lily-Rose Depp, Elisabeth Moss, Natasha Lyonne and Ellen Page
Stars pictured together at a Saint Laurent fashion show in Los Angeles
Singer also says he's well aware that he did some "dumb shit" when he was younger
Record producer signed singer when he was 14
Singer and dance duo Jack Ü releeased 'Where Are Ü Now' last year
'Stitches' makes slow climb to Number One after 17 weeks
Song follows on from singer's recent album 'Purpose'