What is Recursion?

A function that calls itself.

function func() {
  if(/*base case */){ // when to stop the loop
    return something;
  } else { // recursive case
    func(); // call this function
  }
}

Factorial Example

// Factorial (!)
// 4! = 4 * 3 * 2 * 1 = 24
// 3! = 3 * 2 * 1 = 6

function factorial(num) {
  // when to stop the loop
  if (num === 1) {
    return num;
  } else {
    // recursive case
    // call this function
    return num * factorial(num - 1);
  }
}