Get array key in map method

Question

I am comparing two arrays with each other in a function and want to return an array with the highest values at each array key. In my function I have two parameters which both represent an array.

The arrays have the same length and their key values are normal index numbers

Now I just use a normal for loop:

var array1 = [50, 30, 44, 8];
var array2 = [12, 44, 18, 9];

function createList(arr1, arr2){
    for(var x = 0; x < arr1.length; x++){
        arr1[x] = arr1[x] > arr2[x]?arr1[x]:arr2[x];
    }
    return arr1;
}

var highList = createList(array1, array2);

Now I know there are other possiblities of getting this result. But what I was wondering whether you can get the current key in the map method and use that to compare it with another array.

Something in the line of:

var highList = array1.map(function(num){
    return num > array2[keyOfCurrentMap]?num:array2[keyofCurrentMap];
});

Answer 1

var highList = array1.map(function(num, keyOfCurrentMap){
    return num > array2[keyOfCurrentMap]?num:array2[keyofCurrentMap];
});

The second param passed into the callback for map is the key.