获得两个对象的键的交集的最佳方法? [英] Best way to get intersection of keys of two objects?

问题描述

我有两个像这样的对象字面量:

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
}

我想得到这两个对象字面量的键的交集，如下所示:

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

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

我显然可以做一个循环，看看另一个对象中是否存在同名的键，但我想知道这是否是一些函数式编程和映射/过滤/减少使用的好例子?我自己没有做过那么多的函数式编程，但我有一种感觉，对于这个问题，可以有一个干净而聪明的解决方案.

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.

推荐答案

没有indexOf的解决方案.

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>');

O(n) 的第二次尝试.

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>');

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