Arsene Wenger's side had come under criticism from fans and pundits after suffering back-to-back defeats against Manchester City and Chelsea, damaging their bid to finish in the top-four.
Arsenal have been inconsistent this season and were shocked early on when Jack Collison gave Hammers an early lead at the Emirates.
But the Gunners hit back with the equaliser through Lukas Podolski and then claiming all three points scoring four goals in 10 second-half minutes. Giroud scored twice along with Santi Cazorla and Theo Walcott to complete a five star finish in front of their home fans.
Arsenal managed to win after four league matches which moved them to within four points of fourth placed Tottenham.
But could this result mean that Arsenal are getting back to their best? After thrashing Newcastle 7-3 at home, the Gunners lost two in three league games. The Gunners are yet to win against sides above them in the league.
Similar results followed after a comfortable win over Tottenham at home. Wenger's side drew back-to-back matches against Aston Villa and Everton but Swansea City shocked Arsenal with a 2-0 win at the Emirates.
Lurking behind in seventh place Liverpool visit the Emirates next Thursday and although Arsenal won at Anfield at the start of the season, Brendan Rodgers side have improved drastically.