Day 1: Functions

Objective

Today, we’re discussing JavaScript functions. Check out the attached tutorial for more details.

Task

Implement a function named factorial that has one parameter: an integer, n. It must return the value of n! (i.e., n factorial).

Input Format

Locked stub code in the editor reads a single integer, n, from stdin and passes it to a function named factorial.

Constraints

• 1 <= n <= 10

Output Format

The function must return the value of n!.

Sample Input 0

1

4

##Sample Output 0

1

24

Explanation

We return the value of 4! = 4 X 3 X 2 X 1 = 24.

Solutions

Solution 1

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const factorial = n => (n - 1 > 0 ? n * factorial(n - 1) : 1);

Solution 2

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let memoization = [0, 1];

const factorial = n => {
  typeof memoization[n] !== 'number' &&
    (memoization[n] = n - 1 > 0 ? n * factorial(n - 1) : 1);

  return memoization[n];
};