Check if key / value pair exist within another object

Question

If I have the following two objects (Object A and Object B), how can I check if Object B's key/value exists with Object A? In the below example it should return True because both 'make: "Apple"' and 'Model: "iPad"' exists in Object A.

Edit: Object B will be dynamic and may contain only Make or only Model. More keys are added dynamically via checkbox filters.

Is it easier to use a library such as Underscore? If so what functions would be applicable?

I hope this makes sense?

        var a = {
            Make: "Apple",
            Model: "iPad",
            hasScreen: "yes",
            Review: "Great product!",
        }

        var b = {
            Make: "Apple",
            Model: "iPad"
        }

Sorry I edited my answer, it needs to be a dynamic loop somehow — curv, Feb 06 '16 at 17:38
in the case of your edit, `b.Make` would just be undefined and the comparison would just return false. `a.Make === b.Make` still makes sense. — Gustav, Feb 06 '16 at 17:39
Ok cool but what if I added other properties in the future. Any way to make it work for unknown keys? — curv, Feb 06 '16 at 17:42
`function compareKeys(a,b,key){ return a[key] === b[key]; }` or something — Joseph Young, Feb 06 '16 at 17:42
you can find this two posts helpful. http://stackoverflow.com/questions/12160998/compare-two-json-arrays-in-jquery-or-javascript http://stackoverflow.com/questions/20094062/jquery-comparing-and-find-out-the-difference-between-2-json-array — Enrico Acampora, Feb 06 '16 at 18:05

score 3 · Accepted Answer · answered Feb 06 '16 at 17:43

3

Just iterate over all keys and check if the values are equal.

var a = { Make: "Apple", Model: "iPad", hasScreen: "yes", Review: "Great product!" },
    b = { Make: "Apple", Model: "iPad" },
    every = Object.keys(b).every(function (k) {
        return a[k] === b[k];
    });

document.write(every);

answered Feb 06 '16 at 17:43

Nina Scholz

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1

Thanks Nina - perfect... :-) – curv Feb 06 '16 at 17:47

score 2 · Answer 2 · answered Feb 06 '16 at 17:45

2

There’s no builtin way of doing this, but you can use your own implementation (see Nina Scholz’ answer) or Lodash’s _.isMatch function (or Underscore’s _.isMatch):

_.isMatch(a, b)

answered Feb 06 '16 at 17:45

Iso

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Check if key / value pair exist within another object

2 Answers2