A Common-Sense Guide to Data Structures and Algorithms in JavaScript, Volume 1

Reading Recursive Code

It takes time and practice to get used to recursion, and you’ll ultimately learn two sets of skills: reading recursive code and writing recursive code. Reading recursive code is somewhat easier, so let’s get some practice with that first.

We’ll do this by looking at another example: calculating factorials.

A factorial is best illustrated with some examples.

This is the factorial of 3:

3 * 2 * 1 = 6

This is the factorial of 5:

5 * 4 * 3 * 2 * 1 = 120

And so on and so forth.

Here’s a recursive implementation that returns a number’s factorial:

function factorial(number) {
  if (number <= 1) {
    return 1;
  } else {
    return number * factorial(number - 1);
  }
}

This code can look somewhat confusing at first ...