replace an entire array according to a reference table in google app script

I have a spreadsheet with two sheets A and B. Sheet A has two columns, one with the full names of all municipalities in Brazil (around 5500 rows) and another column with its correspondent official codes. Sheet B has three columns to store data regarding an arbitrary event (nearly 8000 rows). One of the columns of sheet B (LOCAL) stores the municipality where the event occured, using the official code for each location (the same official code contained in sheet A). My task is to write a code in google app script language that adds a column to sheet B with the full name of the municipalities, using data in sheet A as a reference.

I hope you will find a solution that does not exceed google spreadsheet run time.