How Sum function with memoization [JAVASCRIPT]

how-sum.js

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

/// The function should return an array containing any combination of
/// elements that add up to exactly the targetSum. If there is no
/// combination that adds up to the targetSum, then return null.

/// If there are multiple combinations possible, you may return any
/// single one.

const howSum = (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;

    // Iterate through numbers array
    for (let num of numbers) {
        const remainder = targetSum - num;
        const remainderResult = howSum(remainder, numbers, memory);
        if (remainderResult !== null) {
            // Store current value in memory.
            memory[targetSum] = [...remainderResult, num];
            // Return value.
            return memory[targetSum];
        }
    }

    // Store current value in memory.
    memory[targetSum] = null;
    // Return value.
    return null;
}

console.log(howSum(7, [2, 3])); // [ 3, 2, 2 ]
console.log(howSum(300, [7, 14])); // null