There is more than one artist with this name.

1) Joker is a 22-year-old programmer/producer from Bristol, UK. Currently producing some of the freshest, most innovative grime instrumentals on the scene but equally embraced by the dubstep world, he mixes influences from Dr. Dre-style G-funk to video game chiptune music to UK bass styles.

2) JOKER (ジョーカー) is a collaboration between 加藤和樹 (Kazuki Kato) and 伊達幸志 (Koji Date).

3) ＪＯＫＥＲ was a visual kei band formed in 2002. They disbanded in 2005.

4) Joker is an indie band from Taichung, Taiwan.

5) Joker is a popular four-piece contemporary covers band based in Plymouth, England.

6) Joker was an English NWoBHM band, which released only one 7", Back on the Road, in 1984.

7) Joker is a Portuguese hard rock band from the '90s formed by Luís Páscoa (drums), Hugo Granger (bass), Tiago Gardner (vocals), José Vasconcelos (keyboard), and Paulo Ferreira (guitar).

8) Joker is a two-person pop/rock band formed in 2006 comprised of Joshua Sellers (in West Memphis, Arkansas) and Angie Bastion (in Christchurch, New Zealand).

9) Joker released their eponymous italo disco LP in 1982 on Good Vibes Records.
http://www.discogs.com/Joker-Joker/release/1237774

10) Joker is also the nom de plume of a member of the OverClocked ReMix community.

11) Joker is a hard rock band from the USA consisting of Tony Ingala (vocals), Nick Sikich (guitar), Joe Miro (guitar/keyboards), Brian Smolar (bass), and Mike Stone (drums).

12) Joker is a hard rock/heavy metal band from Calgary, Alberta, Canada, with one three-song 7" called Not Playing With A Full Deck circa 1993.

13) Joker is a rap artist from Osijek.