In an array with objects, check if a key exists in any of those objects

Question

I have an array of objects, and need to see if a key exists in any of them. Here is what I am doing now:

const arr = [{ id: 1, foo: 'bar' }, { id: 2 }]
arr.map(o => o.foo && true).includes(true)
// true

Is there any better/more accepted way to do this?

Answer 1

You can use Array#some

var arr = [{ id: 1, foo: 'bar' }, { id: 2 }]
result = arr.some(o => 'foo' in o)
console.log(result)

Difference between every() and some()

• every:

It will check for the existence of the given key on all object, and return false if not all of them have this key.

• some:

It will check if at least one object has that key and if there is it already returns true.

Answer 2

const arr = [{ id: 1, foo: 'bar' }, { id: 2 }]
var result = arr.some((value, index) => {
    return value.hasOwnProperty('bar')
});
console.log(result);

Answer 3

I'd use the Array.prototype.some() function:

const arr = [
  { id: 1, foo: 'bar' },
  { id: 2 }
];

var result = arr.some(e => e.hasOwnProperty('foo'));
console.log("The array contains an object with a 'foo' property: " + result);

var result = arr.some(e => e.hasOwnProperty('baz'));
console.log("The array contains an object with a 'baz' property: " + result);

Answer 4

If you just want a true/false to determine if the element is in there, use 'some'. It returns true/false.

const arr = [{ id: 1, foo: 'bar' }, { id: 2 }];
var key = 'foo';
var isInArray= arr.some(function(val, i) {
    return val[i][key];
});

Answer 5

You could use Array#some

var arr = [{ id: 1, foo: 'bar' }, { id: 2 }],
    result = arr.some(o => 'foo' in o);

console.log(result);