Checking for multiple keys in a JavaScript object?

Question

Is there a native or library function for checking multiple keys at once?

Say this is my object:

const foo = {};
foo.superLongNameNeededByPackage = {cat: {black: 1}, hat: 2, bat:3, mat: 12}
console.log(foo);
// { superLongNameNeededByPackage : {cat: {black: 1}, hat: 2, bat:3, mat: 12} }

And I want to check that it has various keys on it, if there a way to do this?

const isReadyForHalloween = hasMultipleKeys(foo.superLongNameNeededByPackage,
  ['cat.black', 'hat', 'bat']);

I'm aware of lodash's has as well as the fact I can write my own using Object.keys and every but I was hoping to avoid it if possible, becuse it would still feel overly verbose and requires writing out the full formulation.

const arr = Object.keys(foo.superLongNameNeededByPackage);
arr.every(item => item.hasOwnProperty("a")
               && item.hasOwnProperty("b")
               && item.hasOwnProperty("c") );

But I don't want to be writing out hasOwnProperty each time, and may want to supply my key list as its own variable.

There is no built-in functionality like that. You can make a custom function or use a third party one, as you mentioned - it should be simple and if you need it in a lot of places, it would ultimately save you time and effort. — VLAZ
– VLAZ, Commented Sep 30, 2019 at 11:33
You can use flatten npm package which allows you to flat the object, it will tranform it into cat.black — Robbin van der Jagt
– Robbin van der Jagt, Commented Sep 30, 2019 at 13:41

Nina Scholz · Accepted Answer · 2019-09-30 11:43:33Z

1

You could take two functions, one to check the path and another to check if all keys are in the object.

function has(object, path) {
    return path.split('.').every(k => object.hasOwnProperty(k) && (object = object[k]));
}

function hasMultipleKeys(object, keys) {
    return keys.every(has.bind(null, object));
}

const foo = {};

foo.superLongNameNeededByPackage = { cat: { black: 1 }, hat: 2, bat: 3, mat: 12 };

const isReadyForHalloween = hasMultipleKeys(foo.superLongNameNeededByPackage,  ['cat.black', 'hat', 'bat']);
console.log(isReadyForHalloween);

answered Sep 30, 2019 at 11:43

Nina Scholz

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Ori Drori · Accepted Answer · 2019-09-30 11:46:33Z

Although lodash doesn't have a built in function, you can create hasMultipleKeys() using _.overArgs().

The function takes the array of keys, and an object you wish to check. The array is passed directly to _.every() (via _.identity()), while the object is applied to _.has() (using _.curry()) to create the predicate for the _.every() function.

const hasMultipleKeys = _.overArgs(_.every, [_.identity, _.curry(_.has)])


const foo = {cat: {black: 1}, hat: 2, bat:3, mat: 12}
  
console.log(hasMultipleKeys(['cat.black', 'hat', 'bat'], foo)) // true
console.log(hasMultipleKeys(['cat.black', 'nothing', 'bat'], foo)) // false

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

jamomani · Accepted Answer · 2021-02-19 18:54:01Z

1

Here is my solution:

> const objectContains = (object, keys) => keys.every(k => k in object)
> const o = { a: 0, b: 1 }
> objectContains(o, ['a', 'b'])
true
> objectContains(o, ['a', 'b', 'c'])
false

answered Feb 19, 2021 at 18:54

jamomani

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Comments

Robbin van der Jagt · Accepted Answer · 2019-09-30 13:46:30Z

0

I had the exact same question a few days ago. This is what I came across. It uses the flat package. https://www.npmjs.com/package/flat

      let foo;
      const obj = flatten(clonedObj, {maxDepth: 0});
      foo = ['yourkeys', 'yourkeys.secondLevel']
        .every(field => obj.hasOwnProperty(field) && !!obj[field]);

answered Sep 30, 2019 at 13:46

Robbin van der Jagt

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