Subset Sum function with memoization [JAVASCRIPT]

can-sum.js

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

/// The function should return a boolean indicating whether or not it
/// is possible to generate the targetSum using numbers from the array.

/// You may use an element of the array as many times as needed.
/// You may assume that all input numbers are nonnegative.

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

    // Return obvious values to stop recursion.
    if (targetSum === 0) return true;
    if (targetSum < 0) return false;

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

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

console.log(canSum(7, [3, 2]));  // prints => true
console.log(canSum(30, [4, 12]));  // prints => false