CODEWITHSUNDEEP
javascriptarrays
BeeNag
BeeNag

Reputation: 1844

manipulating arrays in javascript

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

Upvotes: 0

Views: 96

Answers (4)

Bartek Banachewicz
Bartek Banachewicz

Reputation: 39370

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(keys,values) {
    var result = {};
    for (var i = 0; i < keys.length; i++) {
        result[keys[i]] = values[i];
    }
    return result;
}

With that, our solution becomes:

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

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

Upvotes: 1

isvforall
isvforall

Reputation: 8926

You could use two map functions and some ES6 features:

var newArr = arr2.map(el => el.map((e, i) => ({ [arr1[i]]: e })));

Working example: 

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"] ];

var newArr = arr2.map(el => el.map((e, i) => ({ [arr1[i]]: e })));

document.write('<pre>' + JSON.stringify(newArr, 0, 2) + '</pre>');

Upvotes: 1

Francesco Pezzella
Francesco Pezzella

Reputation: 1795

Using Underscore:

var newArr = _.map(arr2, function(arr) {
    return _.object(arr1, arr);
});

Upvotes: 1

Nina Scholz
Nina Scholz

Reputation: 386560

You could use some array methods like Array#map and Array#forEach.

var arr1 = ["1", "2", "3", "4"],
    arr2 = [["a", "b", "c", "d"], ["e", "f", "g", "h"], ["i", "j", "k", "l"], ["m", "n", "o", "p"], ["q", "r", "s", "t"]],
    newArr = arr2.map(function (a) {
        var o = {};
        arr1.forEach(function (b, i) {
            o[b] = a[i];
        });
        return o;
    });

document.write('<pre>' + JSON.stringify(newArr, 0, 4) + '</pre>');

Upvotes: 1

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