Trying to solve this problem and I don't know where my mistake is!

```js
function findIntersection(strArr) {
  const arr1 =[strArr[0]];
  const arr2 = [strArr[1]];
  const finalArr =[];
  arr1.forEach(e=>{arr2.forEach(element => {
    if(element === e){
      finalArr.push(e);
      console.log(true)
    }
  })})
}

findIntersection(['1, 3, 4, 7, 13', '1, 2, 4, 13, 15']); // => '1,4,13'
findIntersection(['1, 3, 9, 10, 17, 18', '1, 4, 9, 10']); // => '1,9,10'
```