How find the array index for two array comparision and return once array item less than another?

const compareArray = (arr1, arr2) => {  
  let startIndex = 0
  if (arr1[0] < arr2[0]) {
    // find the index from arr1 that is greater than arr2
    startIndex = arr1.findIndex((a, index) => a > arr2[index])
  }

  for (let i = startIndex; i < arr1.length; i++) {
    if (arr1[i] < arr2[i]) {
      return i
    }
  }
}

const exampleArr1 = [15,9,7,5,3,1]
const exampleArr2 = [2,6,8,12,17,22]
const exampleArr3 = [1,2,4,5,15,9,7,5,3]
const exampleArr4 = [2,3,5,6,2,6,8,12,17]

console.log(compareArray(exampleArr1, exampleArr2))
console.log(compareArray(exampleArr3, exampleArr4))