How to know if an array contains an object with a certain 'key'?

Question

Let's say I have this data structure wherein I have an array that contains a set of objects, the objects being 'months'.

monthlySum: [
  {
              jun2018: {
                sales: 0,
                expenses: 0
              } 
            },
            {
              aug2018: {
                sales: 0,
                expenses: 0
              } 
            }
          ]

Now I'd like to know, let's say, if an object with a key of 'sep2018' already exists in this array. If not yet, then I will add a new object with the 'sep2018' key after the last one. If yes, then I will do nothing.

How do I go about doing this?

maybe you consider to use a different data struncture, like an object, instead of an array because you have already grouped by decent key. — Nina Scholz
– Nina Scholz, Commented Jun 10, 2018 at 7:52

Nina Scholz · Accepted Answer · 2018-06-10 07:57:52Z

1

For an update or check, you could use Array#find, which returns either the item or undefined if not found.

function find(array, key) {
    return array.find(object => key in object);
}

var monthlySum = [{ jun2018: { sales: 0, expenses: 0 } }, { aug2018: { sales: 0, expenses: 0 } }];

console.log(find(monthlySum, 'aug2018'));
console.log(find(monthlySum, 'dec2018'));

answered Jun 10, 2018 at 7:57

Nina Scholz

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CertainPerformance · Accepted Answer · 2018-06-10 07:50:26Z

1

You can use .some to check to see if anything in an array passes a certain test:

const monthlySum = [{
    jun2018: {
      sales: 0,
      expenses: 0
    }
  },
  {
    aug2018: {
      sales: 0,
      expenses: 0
    }
  }
];

if (!monthlySum.some((obj) => 'aug2018' in obj)) {
  monthlySum.push({
    aug2018: {
      sales: 0,
      expenses: 0
    }
  })
}
if (!monthlySum.some((obj) => 'sep2018' in obj)) {
  monthlySum.push({
    sep2018: {
      sales: 0,
      expenses: 0
    }
  })
}
console.log(monthlySum);

answered Jun 10, 2018 at 7:50

CertainPerformance

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