function binarySearch(arr, k) {
let left = 0
let right = arr.length - 1
while(left <= right) {
let middle = Math.floor((left + right) / 2)
if(arr[middle] === k) {
return middle
} else if(arr[middle] > k) {
right = middle - 1
} else {
left = middle + 1
}
}
return -1
}
const nums = [6, 17, 25, 34, 52, 63, 85]
const key = 6
console.log(binarySearch(nums, key)) // 输出 0