Merging algorithm.js

var x = [{
    id: 1,
    data: 'ab',
    ordering: 1
}, {
    id: 2,
    data: 'cd',
    ordering: 1
}];

var y = [{
    id: 1,
    data: 'hello',
    ordering: 2
}, {
    id: 2,
    data: 'cd',
    ordering: 1
}, {
    id: 3,
    data: 'pera',
    ordering: 1
}, {
    id: 4,
    data: 'jovica',
    ordering: 1
}];

if (x.length > y.length) {
    longer = x;
    shorter = y;
} else {
    longer = y;
    shorter = x;
}

var final = [];

var longerIds = longer.map((e) => {
    return e.id;
});
var shorterIds = shorter.map((e) => {
    return e.id;
});

var diffed = _.difference(longerIds, shorterIds);
var equalized = _.intersection(longerIds, shorterIds);

if (diffed.length > 0) {
    longer.forEach((e, i) => {
        if (diffed.indexOf(e.id) > -1) {
            final.push(e);
        };
    });
}

longer.forEach((e) => {
    if (equalized.indexOf(e.id) > -1) {
        if (e.ordering > _.find(shorter, { 'id': e.id }).ordering) {
            final.push(e);
        } else {
            final.push(second);
        }
    }
});