Helper function

Have you already noticed the problem?

The program works, miles are calculated, but what happens if Muffin goes all out and decides to fly to a dozen cities more? We will constantly have to copy one part of the code, change the distance, calculate and declare the same variables over and over every time, which violates the rules of the language. Of course, we will cope with the task at hand, but we will spend a lot of time and the code will grow to include hundreds of lines.

Is there a more convenient and competent way to do calculations without copying? There is! Write a function.

A function is a piece of code that can be written once and then reused. A function, unlike a variable, does not simply contain a value, but performs a certain action and solves a certain task: it calculates, compares, searches. For example, our function will calculate miles accrued for the flight.

But first, let’s see what the functions consist of and how they are declared (created) in the code.

var functionName = function () {
  // Actions that are performed
  // by a function or a body
  // of the function
};

functionName is a name of the variable that contains the function. We can access the function using this name and we can use it many times. Let’s assume that the name of a variable is the name of the function.

There are other ways of creating functions, but we’ll discuss them later, in other courses.

Creating function is not more difficult than creating conditions or loops. Use the keyword function, then add parentheses. The curly brackets contain the actions that the function will perform every time we call it. Remember how we did it in the loops? There the code inside { } is called the body of the loop, and here the body of the function.

Write the function calculateMiles for calculating miles.

By the way, note the name calculateMiles. The function literally calculates miles, that is, does something. It’s a common naming convention: the function name contains a verb. This way it is more convenient for developers to navigate their own and even someone else’s code. Maybe the function was written by your colleague and you have no idea what’s inside. It will be enough for you to look at the function name in order to roughly imagine what it is intended for.