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

The Little Fix for Big O

Thankfully, there’s an easy way to eliminate all these extra recursive calls. We’ll call max only once within our code, and save the result to a variable:

function max(array) {
  if (array.length === 0) { return null; }

  if (array.length === 1) { return array[0]; }

  // Calculate the max of the remainder of the array
  // and store it inside a variable:
  const maxOfRemainder = max(array.slice(1));

  // Comparison of first number against this variable:
  if (array[0] > maxOfRemainder) {
    return array[0];
  } else {
    return maxOfRemainder;
  }
}

By implementing this simple modification, we end up calling max a mere four times. Try it out yourself by adding the console.log(’RECURSION’) ...