Sorting Algorithms (bubble sort, merge sort)

Why does the inner loop condition use 'arr.length - i - 1'?

function bubbleSort(arr) {
  for(let i = 0; i < arr.length; i++) {
    for(let j = 0; j < arr.length - i - 1; j++) {
      if(arr[j] > arr[j + 1]) {
        [arr[j], arr[j + 1]] = [arr[j + 1], arr[j]];
      }
    }
  }
  return arr;
}

To ensure array bounds
To skip sorted elements
The inner loop condition optimizes performance by: 1) Reducing unnecessary comparisons, 2) After each pass, largest element is in place, 3) Subsequent passes can skip last i elements, 4) Decreases inner loop range progressively, 5) Avoids comparing already sorted elements, 6) More efficient than checking entire array each time, 7) Common optimization in bubble sort implementations, 8) Reduces total number of comparisons significantly.
To improve performance
To handle edge cases

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