Finding the differences between two JavaScript Objects-CodePudding

Yes, there's a plethora of questions with titles similar to this and I can assure you I've tested almost all of them. Everything Google threw at me, I tried. None sufficed.

Considering these two objects:

const o1 = {
  "someProperty": "someValue",
  "anotherProperty": {
    "p1": "v1",
    "p2": "v2"
  }
}

const o2 = {
  "anotherProperty": {
    "p1": "v1",
    "p2": "v2"
  }
}

How do I find the differences between o2 and o1, by top-level keys, I believe, without "destroy" the object by setting properties' values as undefined (honestly, I found that answer, here, preposterous).

Why do I need this? The here depicted o1 contains "all data" and o2 a subset that will be removed so I can perform an update. You can think of if as the inverse of an intersection.

In pseudo-code above, all I want as output is:

const diff = {
  "someProperty": "someValue"
}

Of course, this is an oversimplified example, in the real deal I have many other properties, with different values, always of primitive data-tyes (plain text, integers, booleans...) one-level nested (like o2) or deep down more levels, but always primitive types.

Sounds like a very simple thing but I just couldn't find anything without NodeJS, Lodash, Underscore or whatever other 3rd-party library.

CodePudding user response：

You could get the entries and check against. For objects perform the same and check if the result has some keys.

const
    getDifference = (a, b) => Object.fromEntries(Object
        .entries(a)
        .reduce((r, [k, v]) => {
            if (v && typeof v === 'object') {
                let temp = getDifference(v, b[k] || {});
                if (Object.keys(temp).length) r.push([k, temp]);
            } else {
                if (v !== b[k]) r.push([k, v]);
            }
            return r;
        }, [])
    ),
    o1 = { someProperty: "someValue", anotherProperty: { p1: "v1", p2: "v2", p3: 'v3' }, n1: { n2: { n3: 42 } } },
    o2 = { someProperty: "someValue", anotherProperty: { p1: "v1", p2: "v2" } },
    o3 = { anotherProperty: { p1: "v1", p2: "v2" } };

console.log(getDifference(o1, o3));
console.log(getDifference(o2, o3));

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