Recursive Binary Search

searching.js

// ES6 Arrow Function
const binarySearch = (arr, k) => {
    let start = 0, end = arr.length - 1, mid;
    mid = Math.floor((start + end) / 2);
    if(arr.length === 1 && arr[0] === k) return -1;
    if(arr[mid] === k) return mid;

    if(arr[mid] > k) {
        return binarySearch(arr.slice(0, mid), k);
    } else {
        return binarySearch(arr.slice(mid));
    }
}

// let testArray = [1, 2, 3, 4, 5, 6, 7, 8];
// let x = 8;
// binarySearch(testArray, x);
// output => 7