Loop is the basic construction in each programming language. All repeatable operations are being done using loops. I think you know how the basic loops like while, do and for work and when you should use one of them. But are you sure? Maybe should you use array functions?
How many of your operations in a loop rely on building objects based on the value? Or selecting only a few items from the array using a predicate? Maybe you use array values to calculate something? Whatever you do, read why you should replacing basic loops by array operations.