"Good morning, Las Vegas!" says Nick van de Wall, better known as Afrojack. It is 1 a.m., but the night still rages at Surrender, a nightclub in Encore. Several hundred revelers have waited two hours for this 23-year-old rising star to appear, chanting “Afrojack! Afrojack!” The warm-up act, DJ Milo “Mighty Mi” Berger, has just finished building anticipation to a frenzy by deftly weaving a contemporary electronic pop mix while dropping remixes and “edits”—old pop chestnuts retrofitted with a post-millennial beat—of classics such as Madonna’s “Holiday.”