Describe the narrator in "A & P." Why has Updike chosen this kind of narrator for his story?

The narrator in this story is Sammy, the nineteen year old boy who works at the A & P at the checkout line. 

"Sammy narrates this story in the first person. His voice is colloquial and intimate. His speech is informal, a factor that highlights his individuality and propensity to question authority."

The author uses Sammy as the narrator so that the reader can experience the events in the store through his eyes.  The narrator gives the reader a colorful accounting of what is going on in the store, describing the usual shoppers, women, housewives as sheep. 

The author uses Sammy as the narrator because:

"Young people seem to identify with Sammy and respond to the way he tells his story."

The perception of the narrator is that of a young person looking at the adult world and finding fault with it, making fun of what grownups to and how they do it.  He is critical with a cynical tone in the story.  He is bored with his job, the only amusement he has is to make fun of the customers in his mind. 

He feels like he hit the jackpot when three girls, dressed only in bathing suits, come into the store.  Sammy can't take his eyes off of them, they completely throw him off balance.