Solution Review: Search the First Occurrence of a Number

function firstIndex(arr, testVariable, currentIndex) { // returns the first occurrence of testVariable
  
  while (currentIndex < arr.length) { // Iterate over the array
    if (arr[currentIndex] == testVariable) {  // Return the current index if testVariable found
      return currentIndex;
    } 
    currentIndex += 1;
  }
  return -1;
}
// Driver Code
var arr = [9, 8, 1, 8, 1, 7];
var testVariable = 1;
var currentIndex = 0;
console.log(firstIndex(arr, testVariable, currentIndex));