mergeArrays

function mergeArray(firstArray, secondArray) {
    let newArray = new Array(firstArray.length).fill(0);
    for (let index = 0; index < firstArray.length; index++) {
        if (index % 2 === 0) {
            newArray[index] = Number(firstArray[index]) + Number(secondArray[index]);
        } else {
            newArray[index] = firstArray[index] + secondArray[index];
        }
    }
    console.log(newArray.join(' - '));
}