manipulating arrays in javascript

Question

I have two arrays like so

var arr1 = ["1", "2", "3", "4"];

var arr2 = [["a", "b", "c", "d"], ["e", "f", "g", "h"], ["i", "j", "k", "l"], ["m", "n", "o", "p"], ["q", "r", "s", "t"]];

What I would like to do is merge the two arrays to form a final output that looks like this

var newArr = [{1: "a", 2: "b", 3: "c", 4: "d"}, {1: "e", 2: "f", 3: "g", 4: "h"}, {1: "i", 2: "j", 3: "k", 4: "l"}, {1: "m", 2: "n", 3: "o", 4: "p"}, {1: "q", 2: "r", 3: "s", 4: "t"}];

So effectively take each array out of the second array and then merge it with the first array to form an object.

I was just wandering what the most efficient way to do this in javascript would be?

Any help would be much appreciated

Thanks for your time

Answer 1

Assuming the input always matches, I'd start with arr2:

arr2.map(x =>

However, at this point what you want is to zip values from x and the corresponding values from y together, so let's introduce a helper first (I'm actually gonna call it zipKeyVal¹ because it maps values from first param to keys, and the second to values).

function zipKeyVal(a,b) {
    var result = {};
    for (var i = 0; i < a.length; i++) {
        result[a[i]] = b[i];
    }
    return result;
}

With that, our solution becomes:

var newArr = arr2.map(x => zipKeyVal(arr1, x));

¹_{Oh, apparently underscore.js calls that _.object, and lodash zipObject.}