My opinion on recursion vs while (in general)

recursion-vs-while.js

#!/usr/bin/env node

// 0 is even, 1 is odd, and N is even if N-2 is even

/*
Which one is easier to read and understand for you? (Subjectively)
Which one is significantly safer (aka, what could go wrong)? (Objectively)

I found 4 scenarios that would crash the less safe one where the safer one
will return "undefined". Did I miss any?
*/

const recursiveIsEven = function(num) {
    // Convert negative numbers to positive
    if (num < 0) {
        num = -num;
    }
    if (num == 0) {
        return "Even";
    }
    if (num == 1) {
        return "Odd";
    }

    return recursiveIsEven(num - 2);
};

const whileIsEven = function(num) {
    // Convert negative numbers to positive
    if (num < 0) {
        num = -num;
    }

    while (num >= 0) {
        if (num == 0) {
            return "Even";
        }
        if (num == 1) {
            return "Odd";
        }

        num = num -2;
    }
};

console.log(recursiveIsEven(9));
console.log(recursiveIsEven(-14));
console.log(whileIsEven(9));
console.log(whileIsEven(-14));