Product Array coding problem

My solution to a “Daily Coding Problem” that I received in my mail today.

Given an array of integers, return a new array such that each element at index i of the new array is the product of all the numbers in the original array except the one at i.

For example, if our input was [1, 2, 3, 4, 5], the expected output would be [120, 60, 40, 30, 24]. If our input was [3, 2, 1], the expected output would be [2, 3, 6].

Follow-up: what if you can’t use division?

Here’s my non optimal solution in Javascript,

function product(inputArr) {
    if(inputArr ===  null || inputArr === undefined) {
        //return an empty array
        return [];
    }
    let productArray = []; 
    for(let i=0; i < inputArr.length; i++) {
        let product = 1;
        for(let j=0; j < inputArr.length; j++) {
            if( j === i) {
                //if at the same index, we skip it
                continue;
            }
            //what if there's a 0 value in the array?
            product *= inputArr[j];
        }
        productArray[i] = product;
        product = 1;
        //or we can also do productArray[i] = product
    }
    return productArray;
}

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