The function returns products of element in an array

productOfArray.js

//Given an integer array nums, 
//write a function that returns an array products,
//such that each entry at position i, in products is a product of all the other elements in nums except num[i]
// #algorithm friday set4


const productOfArray = (nums) => {
//  testing for array or empty array
   if (!Array.isArray(nums)  || nums.length == 0 ) return ' Invalid Input '

  let count = nums.length  
  let start = new Array(count);
  let end = new Array(count);
  let product = new Array(count);
  
//   setting the intials of the array
     start[0] = 1;
     end[count-1] = 1   

// the start array
    for (let i = 1; i < count; i++){
        start[i] = nums[i - 1] * start[i - 1];
     }
// the end array        
    for (let j = count - 2; j >= 0; j--){
         end[j] = nums[j + 1] * end[j + 1];
     }
//  the product array = start * end
    for (let i = 0; i < count; i++){
         product[i] = start[i] * end[i];
    }
        return product
}

console.log(productOfArray([4,5,10,2])) //return [ 100, 80, 40, 200 ]

Thanks a lot for the feedback,
I have been pondering over it for some time, so far this is what I have been able to come up with, hopefully in due time, I will be able to come with a more memory efficient approach..