Merge Sorted Arrays

function mergeSortedArrays(array1,array2){
    const mergedArray = [];
    let array1Item = array1[0];
    let array2Item = array2[0];
    let i = 1;
    let j = 1;
    
    //Check input
    if (array1.length === 0){
        return array2;
    }
    if (array2.length === 0){
        return array1;
    }
    while (array1Item || array2Item){
        console.log(array1Item, array2Item)
        if(!array2Item || array1Item < array2Item){
            mergedArray.push(array1Item)
            array1Item = array1[i];
            i++;
        }else{
            mergedArray.push(array2Item);
            array2Item = array2[j];
            j++;
        }
    }
    console.log(mergedArray)
    return mergedArray;
}
mergeSortedArrays([0,4,7],[1,3,5,8])