Question

71

Best way to get intersection of keys of two objects?

rated 0 times [ 72] [ 1] / answers: 1 / hits: 43208 / 9 Years ago, mon, december 21, 2015, 12:00:00

I have two object literals like so:

var firstObject =

{

    x: 0,

    y: 1,

    z: 2,



    a: 10,

    b: 20,

    e: 30

}



var secondObject =

{

    x: 0,

    y: 1,

    z: 2,



    a: 10,

    c: 20,

    d: 30

}

I want to get the intersection of the keys these two object literals have like so:

var intersectionKeys  = ['x', 'y', 'z', 'a']

I can obviously do a loop and see if a key with the same name exists in the other object, but I am wondering if this would be a good case for some functional programming and map / filter / reduce usage? I myself have not done that much functional programming, but I have a feeling, that there could exist a clean and clever solution for this problem.

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kiyam

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4 Years ago

answered 9 Years ago devinjadong · Accepted Answer

A solution without indexOf.

var firstObject = { x: 0, y: 1, z: 2, a: 10, b: 20, e: 30 },

    secondObject = { x: 0, y: 1, z: 2, a: 10, c: 20, d: 30 };



function intersection(o1, o2) {

    return Object.keys(o1).concat(Object.keys(o2)).sort().reduce(function (r, a, i, aa) {

        if (i && aa[i - 1] === a) {

            r.push(a);

        }

        return r;

    }, []);

}



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

Second attempt with O(n).

var firstObject = { x: 0, y: 1, z: 2, a: 10, b: 20, e: 30 },

    secondObject = { x: 0, y: 1, z: 2, a: 10, c: 20, d: 30 };



function intersection(o1, o2) {

    return Object.keys(o1).filter({}.hasOwnProperty.bind(o2));

}



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