One can argue that in the short story, A&P, John Updike uses foreshadowing to hint towards the fact that it's expected for Sammy, the main character or protagonist, to quit his job by the end of the story. After re-reading the story for a second time one can pick up subtle hints and clues that indicate Sammy quitting. One can interpret these clues or hints as Sammy just hating his job, but if you continue to analyze said hints and clues you come to the same conclusion, it is inevitable that he is going to quit.
At the beginning of the story it starts off with Sammy noticing three girls walking into the store as he rings up a customer. Updike is descriptive to portray an image to the reader of how Sammy sees these girls when they first walk in, and how he is dealing with the customer he seems to hate. "I ring it up again and the customer starts giving me hell." After reading this line one can assume since Sammy calls it hell he obviously hates it, someone does not refer to something as hell if they enjoy it. He goes on to say she is a witch who would have been burned at the stake if she lived during the times of The Salem Witch Trials. One can interpret this as him no respecting the customers. Another example of this is when Updike writes, "The sheep pushing their carts down the aisle  were pretty hilarious." The sheep being the customers and that is Sammy's way of not considering the customers people, he does not respect them. Just by him saying all of this one can assume the Sammy hates his job, and he is just hanging by thread waiting for one more reason to quit.
At this point in the story Sammy already discards the customers as not being people and shows the reader how he despises his job. He only continues to do so throughout the story. For example, "I bet you could set off dynamite in an A&P and the people would by and large keep reaching and checking oatmeal off their lists and muttering 'Let me see, there was a third thing, began with A, asparagus, no, ah, yes, applesauce!' or whatever it is they mutter.