Best Sum function with memoization [JAVASCRIPT]

best-sum.js

/// Write a function 'bestSum(targetSum, numbers)' that takes in a
/// targetSum and an array of numbers as arguments.

/// The function should return an array containing the shortest
/// combination of numbers that add up to exactly the targetSum.

/// If there is a tie for the shortest combination, you may return any
/// one of the shortest.

const bestSum = (targetSum, numbers, memory = {}) => {
    // Check in memory.
    if (targetSum in memory) return memory[targetSum];

    // Return obvious values to stop recursion.
    if (targetSum === 0) return [];
    if (targetSum < 0) return null;

    let shortestCombination = null;

    // Iterate through numbers array
    for (let num of numbers) {
        const remainder = targetSum - num;
        const remainderCombination = bestSum(remainder, numbers, memory);
        if (remainderCombination !== null) {
            const combination = [...remainderCombination, num];
            // If the combination is shorter than the current 'shortest', update it.
            if (shortestCombination === null || combination.length < shortestCombination.length) {
                shortestCombination = combination;
            }
        }
    }

    // Return value.
    memory[targetSum] = shortestCombination;
    return shortestCombination;
}

console.log(bestSum(7, [5, 3, 4, 7])); // [7]
console.log(bestSum(8, [1, 4, 5])); // [4, 4]
console.log(bestSum(100, [1, 2, 5, 25])); // [25, 25, 25, 25]