Get value from array key and build a new array

Question

I cannot get the value of 'Date' key to build my array.

const input = [{
  "Date": "12/08/2020",
  "Day": "Wednesday"
}, {
  "Date": "13/08/2020",
  "Day": "Thursday"
}, {
  "Date": "14/08/2020",
  "Day": "Friday"
}];

function get(o, days) {
  const weekdays = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
  const [dd, mm, yyyy] = Object.keys(o)[0].split('/');
  const date = new Date(`${yyyy}-${mm}-${dd}`);

  date.setUTCDate(date.getUTCDate() + days);

  const key = `${
    `${date.getUTCDate()}`.padStart(2, '0')
    }/${
    `${(date.getUTCMonth() + 1)}`.padStart(2, '0')
    }/${
    date.getUTCFullYear()
    }`;
  const value = weekdays[date.getUTCDay()];

  return {
    [key]: value
  };
}

function prepend(array, count) {
  while (count-- > 0) {
    array.unshift(get(input[0], -1));
  }
}

function append(array, count) {
  while (count-- > 0) {
    array.push(get(input[input.length - 1], 1));
  }
}

prepend(input, 1);
append(input, 1);
console.log(input);

The console shows this output:

{NaN/NaN/NaN: undefined},{Date: "12/08/2020", Day: "Wednesday"},{Date: "13/08/2020", Day: "Thursday"},{Date: "14/08/2020", Day: "Friday"},{NaN/NaN/NaN: undefined}

Seems like the problem is with Object.keys(o)[0]. How can I fix this?

There's no JSON in this question, just arrays and objects. Might help with your searching if you leave off "json" from your search terms. — Heretic Monkey
– Heretic Monkey, Commented Aug 12, 2020 at 20:28
I guess you want o[Object.keys(o)[0]] instead of Object.keys(o)[0] or simply o.Date since you know the key already. — Berk Kurkcuoglu
– Berk Kurkcuoglu, Commented Aug 12, 2020 at 20:28
I want to use o.Date and tried but it didn't bring any results. Would you be able to amend my code please? — qqruza
– qqruza, Commented Aug 12, 2020 at 20:29
If you replace Object.keys(o)[0] in the code above with o.Date, the code works as I would expect it. — Heretic Monkey
– Heretic Monkey, Commented Aug 12, 2020 at 20:32

Unmitigated · Accepted Answer · 2020-08-12 20:34:32Z

1

You actually want the first value, not the first key.

const [dd, mm, yyyy] = Object.values(o)[0].split('/');

However, since you already know the name of the key, you can simply use o.Date.

const [dd, mm, yyyy] = o.Date.split('/');

answered Aug 12, 2020 at 20:34

Unmitigated

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1 Comment

qqruza Over a year ago

Thank you and to @Heretic-Monkey. Thank you so much!

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