题解 | #查找数组元素位置#

二分查找方法

其时间复杂度: O(log2n)

function indexOf(arr, item) {
    let left = 0,
        mid,
        right = arr.length - 1;
    while(left <= right) {
        mid = parseInt((left + right) / 2)
        if(item  == arr[mid]) {
            return mid
        } else if(item > arr[mid]) {
            left = mid + 1
        } else  {
            right = mid - 1
        }
    }

    return -1
}