二分法 binary_search

const binarySearch = (arr, key) => {
    let low = 0, high = arr.length - 1;
    while(low <= high){
        let mid = Math.floor((low + high) / 2)
        let guess = arr[mid]
        if(guess === key){
            return mid
        }
        if(guess > key){
            high = mid - 1
        }else{
            low = mid + 1
        }
    }
    return -1
}