Introduction to functional programming

So far in this book, we have used a paradigm called imperative programming. In imperative programming, we code each step of the program, describing in detail what needs to be done and in which order it needs to be done.

In this topic, we will introduce a new paradigm called functional programming. Functional programming was a paradigm used especially by academics, and thanks to modern languages such as Python and Ruby, it started becoming popular among industry developers as well. And thankfully, we can use JavaScript to program functionally, leveraging its ES6 capabilities as well.

Functional versus imperative programming

Developing in the functional paradigm is not difficult; it is just a matter of getting used to how the paradigm works. Let's code an example to note the differences.

Consider that we need to print all the elements of an array. We can use imperative programming and declare the following function:

var printArray = function(array){ 
...