A Common-Sense Guide to Data Structures and Algorithms

Recurse Instead of Loop

Let’s say you work at NASA and need to program a countdown function for launching spacecraft. The particular function that you’re asked to write should accept a number—such as 10—and display the numbers from 10 down to 0. Take a moment and implement this function in the language of your choice. When you’re done, read on.

Odds are that you wrote a simple loop, along the lines of this JavaScript implementation:

function countdown(number) {
  for(var i = number; i >= 0; i--) {
    console.log(i);
  }
}
countdown(10);

There’s nothing wrong with this implementation, but it may have never occurred to you that you don’t have to use a loop.

How?

Let’s try recursion instead. Here’s a first attempt at using recursion to ...