binary search using for loop in javascript

Question

I am trying to implement binary search using for loop in javascript but it fails some of the test cases, below is my code

function binarySearch(arr, val){
    let start = 0
    let end = arr.length - 1
    let middle = Math.floor((start + end)/2)

    for(let i = start; i<= end; i++){
        if(val === arr[middle]) { 
           return middle
        }

        if(val < arr[middle]){
            end = middle - 1
        }

        if(val > arr[middle]){
           start = middle + 1
        }

        middle = Math.floor((start + end)/2)
    }
        return -1
  }

    // test case:1 console.log(binarySearch([5, 6, 9, 10, 13, 14, 18, 30, 34, 35, 37, 40, 44, 64, 79, 84, 86, 95, 96, 98, 99], 9))
    
    
   // test case:2 console.log(binarySearch([1,3,4,5,6,7,8,9, 10], 10))

It passes the 2nd test case but miserably fails the 1st one. Can anyone throw some light, please?

Answer 1

I realized why not use "for loop" in this case.

It is because inside the loop I'm assigning "start" a new value but problems arise when you come across the fact that the value of "i" remains the same previously initialized "start" value.

The same occurs with, i <= end

I mean "i" is not reassigned anything other than i++. I've realized the fact that under these situations it's better to go with the while loop iteration instead of for loop where you need to reinitialize index from inside the loop.