# Multiply Strings - [Leetcode] with JavaScript

I’ve been tacking this problem far too long and I can’t seem to find what is wrong with my logic.

Prompt:

Given two non-negative integers num1 and num2 represented as strings,
return the product of num1 and num2.

Note:

The length of both num1 and num2 is < 110.

Both num1 and num2 contains
only digits 0-9.

Both num1 and num2 does not contain any leading zero.

You must not use any built-in BigInteger library or convert the inputs
to integer directly.

Here is my attempt:

``````var multiply = function(num1, num2) {
var result = 0;
// if any of the nums is 0, automatically it is zero
if(num1 === '0' || num2 === '0') {return'0'};

var length1 = num1.length - 1;
var length2 = num2.length - 1;
var counterI = 0;
var iBase10 = 1;
for(var i = length1; i >= 0; i--){
iBase10 = Math.pow(10, counterI)
counterI++;
var counterJ = 0
var jBase10 = 1;
for(var j = length2; j >= 0; j--){
jBase10 = Math.pow(10, counterJ)
counterJ++;
result += (num1[i] * iBase10) * (num2[j] * jBase10)
}
}
return result.toString()
};
``````

Essentially the logic is that I can adding `result` each multiplication I make starting from the right side of the strings to the left (to all possible combination, hence the nested for loop).

As the indexes moves to the left, the `base10` is increased to power of 10 so each calculation is set accordingly.

However, I can’t seem to find what is wrong when I type in as follows:

`var result = multiply("123456789","987654321")`

The result I get is `121932631112635260`, yet the actual answer is `121932631112635269`

I’m so slightly close the answer!