It was the final track Ariana performed on Monday.
The song is being streamed and downloaded after a fan campaign to get the track to the top of the official charts.
The track has climbed from outside the top 200 overnight to number 35 and it's currently outselling Justin Bieber and Liam Payne on iTunes.
However iTunes sales no longer contribute greatly to chart positions, with the top 40 more influenced by listeners' streaming habits.
