Introduction

In the previous chapter, we looked at variables and values and how we can temporarily store data in a variable and make changes to that data. We’re now going to look at how we can use that data to run logic in code, or not, selectively. “Logic” refers to the sequence of instructions that control how your program operates or processes data. This logic allows you to control how data flows through your software. You can react to and perform different operations based on the values in your variables.

The logic could be for validating your user’s inputs. If we were writing code to manage a bank account and the user asked to withdraw some money, we could check that they asked for a valid amount of money. We would check that they had enough money in their account. If the validation were successful, we would use logic to update their balance, transfer the money, and show a success message. If the validation failed, we’d show a message explaining...