For loops nested inside each other

Question

I'm trying to write a script that will return me all possible combinations for some parameters. Here is what I currently have. The problem is that length of tagsLoop list can change and then I would need another for loop inside the most nested loop. And then another one and another one. I'm adding screenshot with variables that I use to loop over.

Edit: added working snippet

 var tagsLoop = ["mobile_size", "desktop_size", "tag_test"]
 var bigArray = [{tag: "mobile_size", key: "size", val: "6"},
    {tag: "mobile_size", key: "size", val: "2"},
    {tag: "desktop_size", key: "size", val: "10"},
    {tag: "desktop_size", key: "size", val: "20"},
    {tag: "tag_test", key: "oracle", val: ""},
    {tag: "tag_test", key: "pros", val: ""}]

        for (var i = 0; i < bigArray.length; i++) {
            if (bigArray[i]['tag'] == tagsLoop[0]) {
                var part1 = bigArray[i]['key'] + '=' + bigArray[i]['val']

                for (var j = 0; j < bigArray.length; j++) {
                    if (bigArray[j]['tag'] == tagsLoop[1]) {
                        var part2 = "&" + bigArray[j]['key'] + '=' + bigArray[j]['val']

                        for (var k = 0; k < bigArray.length; k++) {

                            if (bigArray[k]['tag'] == tagsLoop[2]) {


                                var part3 = "&" + bigArray[k]['key'] + '=' + bigArray[k]['val']


                                console.log(part1, part2, part3)
                            }
                        }
                    }
                }
            }
        }

If you need an arbitrary depth, that usually suggests that you need recursion. If you google "variable number of nested for loops", your should be able to find examples. — Carcigenicate
– Carcigenicate, Commented Sep 7, 2018 at 15:30
Why should tagLoop change during your iterations? And what does it mean? — Federico klez Culloca
– Federico klez Culloca, Commented Sep 7, 2018 at 15:32
@FedericoklezCulloca it doesn't change during the iteration, but it depends on user output. so it may change over time. Sorry for not making it clear. — AlienDeg
– AlienDeg, Commented Sep 7, 2018 at 15:32
@asynts yep, sorry for that. forgot about variables. added now. — AlienDeg
– AlienDeg, Commented Sep 7, 2018 at 15:38

Nina Scholz · Accepted Answer · 2018-09-07 16:06:36Z

You could get the grouped data first and the build new arrays with the combinations of the wanted items and their values.

function getCartesian(array, keys) {
    var temp = array.reduce((r, { tag, key, val }) => {
            (r[tag] = r[tag] || []).push([key, val].join('='));
            return r;
        }, Object.create(null));

    return keys
        .map(k => temp[k])
        .reduce((a, b) => a.reduce((r, v) => r.concat(b.map(w => [].concat(v, w))), []))
        .map(a => a.join('&'));
}

var array = [{ tag: "mobile_size", key: "size", val: "6" }, { tag: "mobile_size", key: "size", val: "2" }, { tag: "desktop_size", key: "size", val: "10" }, { tag: "desktop_size", key: "size", val: "20" }, { tag: "tag_test", key: "oracle", val: "" }, { tag: "tag_test", key: "pros", val: "" }],
    tags = ["mobile_size", "desktop_size", "tag_test"],
    result = getCartesian(array, tags);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

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