Javascript Program for Find lost element from a duplicated array

// Javascript program to find missing element from
// same arrays (except one missing element)

/* Function to find missing element based
on binary search approach. arr1[] is of
larger size and N is size of it.arr1[] and
arr2[] are assumed to be in same order. */
function findMissingUtil(arr1, arr2, N) {

    // special case, for only element
    // which is missing in second array
    if (N == 1)
        return arr1[0];

    // special case, for first
    // element missing
    if (arr1[0] != arr2[0])
        return arr1[0];

    // Initialize current corner points
    let lo = 0, hi = N - 1;

    // loop until lo < hi
    while (lo < hi) {
        let mid = parseInt((lo + hi) / 2, 10);

        // If element at mid indices are
        // equal then go to right subarray
        if (arr1[mid] == arr2[mid])
            lo = mid;
        else
            hi = mid;

        // if lo, hi becomes
        // contiguous, break
        if (lo == hi - 1)
            break;
    }

    // missing element will be at hi
    // index of bigger array
    return arr1[hi];
}

// This function mainly does basic error
// checking and calls findMissingUtil
function findMissing(arr1, arr2, M, N) {
    if (N == M - 1)
        console.log("Missing Element is " + findMissingUtil(arr1, arr2, M));
    else if (M == N - 1)
        console.log("Missing Element is " + findMissingUtil(arr2, arr1, N));
    else
        console.log("Invalid Input");
}

let arr1 = [1, 4, 5, 7, 9];
let arr2 = [4, 5, 7, 9];
let M = arr1.length;
let N = arr2.length;
findMissing(arr1, arr2, M, N);

// Javascript program to find 
// missing element from one array
// such that it has all elements 
// of other array except one.
// Elements in two arrays
// can be in any order.

// This function mainly does XOR 
// of all elements
// of arr1[] and arr2[]
function findMissing(arr1, arr2, M, N) {
    if (M != N - 1 && N != M - 1) {
        console.log("Invalid Input");
        return;
    }

    // Do XOR of all element
    let res = 0;
    for (let i = 0; i < M; i++)
        res = res ^ arr1[i];
    for (let i = 0; i < N; i++)
        res = res ^ arr2[i];

    console.log("Missing element is " + res);
}

let arr1 = [4, 1, 5, 9, 7];
let arr2 = [7, 5, 9, 4];

let M = arr1.length;
let N = arr2.length;

findMissing(arr1, arr2, M, N);