how to merge two sorted array in one sorted array in JavaScript without using sort()

Question

In this program merged two array and then sorted using temp.but this not correct method.because two array are sorted ,so method should be unique i.e. merging of two sorted i

Answer 1

function mergeArrays(arr1, arr2) {

    if (!arePopulatedArrays(arr1, arr2))
        return getInvalidArraysResult(arr1, arr2);

    let arr1Index = 0;
    let arr2Index = 0;
    const totalItems = arr1.length + arr2.length;
    const mergedArray = new Array(totalItems);

    for (let i = 0; i < totalItems; i++) {

        if (hasItems(arr1, arr1Index)) {

            if (hasItems(arr2, arr2Index)) {

                if (HasSmallestItem(arr1, arr2, arr1Index, arr2Index)) {
                    mergedArray[i] = arr1[arr1Index++];
                } else {
                    mergedArray[i] = arr2[arr2Index++];
                }
            } else {
                mergedArray[i] = arr1[arr1Index++];
            }
        } else {
            mergedArray[i] = arr2[arr2Index++];
        }
    }
    return mergedArray;
}

function arePopulatedArrays(arr1, arr2) {

    if (!arr1 || arr1.length === 0)
        return false;

    if (!arr2 || arr2.length === 0)
        return false;

    return true;
}

function getInvalidArraysResult(arr1, arr2) {

    if (!arr1 && !arr2)
        return [];

    if ((!arr2 || arr2.length === 0) && (arr1 && arr1.length !== 0))
        return arr1;

    if ((!arr1 || arr1.length === 0) && (arr2 && arr2.length !== 0))
        return arr2;

    return [];
}

function hasItems(arr, index) {
    return index < arr.length;
}

function HasSmallestItem(arr1, arr2, arr1Index, arr2Index) {
    return arr1[arr1Index] <= arr2[arr2Index];
}