Simple recursion example

Recursion.js

/*
  Make a function that computes a factorial recursively.
  A factorial is when you take a number n and multiply by each preceding integer until you hit one.
  n * (n-1) * (n-2) ... * 3 * 2 * 1
  
  Call the function factorial
  
  factorial(1) = 1
  factorial(2) = 2
  factorial(3) = 6 
*/
const factorial = (n) => {
  if (n === 0) return 1;
  return n * factorial(n-1);
}


// Jasmine unit tests
// do not modify the below code
describe('factorial', function() {
  it('should do factorials', () => {
    expect(factorial(1)).toEqual(1);
    expect(factorial(2)).toEqual(2);
    expect(factorial(3)).toEqual(6);
    expect(factorial(10)).toEqual(3628800);
  });
});