Binary Search Algorithm using JavaScript

let myArray = [1, 2, 3, 4, 5, 6, 7, 8, 9];

function binarySearch(arr, element) {

  let result = true;
  let firstIndex = 0;
  let lastIndex = arr.length - 1;

  while (firstIndex <= lastIndex) {

    let mid = (firstIndex + lastIndex)/2;

    if (arr[mid] === element) {

      result = false;
      return `Element ${element} found in index ${mid}`;

    }
  else if (element < arr[mid]) {

      lastIndex = mid - 1;

    }
 else {

      firstIndex = mid + 1;

    }
  }

  if (result) {

    return `Element ${element} is not found`;

  }
}
console.log(binarySearch(myArray, 5));