Recursion Problem Set (easy)

power(n, x)

Write a function called power which accepts a base and an exponent. The function should return the power of the base to the exponent. This function should mimic the functionality of Math.pow() - do not worry about negative bases and exponents.

const power = (n, x) => {
  if (x == 0) return 1;
  if (x == 1) return n;
  let t = power(n, Math.floor(x / 2));
  return t * t * power(n, x % 2);
};

factorial(n)

Write a function factorial which accepts a number and returns the factorial of that number. A factorial is the product of an integer and all the integers below it; e.g., factorial four (4!) is equal to 24, because 4 * 3 * 2 * 1 equals 24. factorial zero (0!) is always 1.

const factorial = n => {
  if (n == 0) return 1;
  return n * factorial(n - 1);
};

productOfArray(arr)

Write a function called productOfArray which takes in an array of numbers and returns the product of them all.

const productOfArray = arr => {
  if (arr.length == 0) return 1;
  return arr[0] * productOfArray(arr.splice(1));
};

recursiveRange(num)

Write a function called recursiveRange which accepts a number and adds up all the numbers from 0 to the number passed to the function.

const recursiveRange = num => {
  if (num == 0) return 0;
  return num + recursiveRange(num - 1);
};

fib(num)

Write a recursive function called fib which accepts a number and returns the nth number in the Fibonacci sequence. Recall that the Fibonacci sequence is the sequence of whole numbers 1, 1, 2, 3, 5, 8, which starts with 1 and 1, and where every number thereafter is equal to the sum of the previous two numbers.

const fib = num => {
  if (num == 1 || num == 2) return 1;
  return fib(num - 1) + fib(num - 2);
};