Higher Order Functions

Throughout this chapter, we have leveraged the fact that JavaScript functions can be passed around just like any other value. We say that functions are first-class citizens in JavaScript, which means that they are treated equally to other types.

Thanks to their first-class citizenry, functions can be combined together, rendering programs even more expressive and enabling a truly functional programming style. A function that takes another function as a parameter or returns another function is called a higher-order function. Check out this final version of our example program.