Check how many elements of an array exists as keys in an object in javascript

Question

I have an object

const Obj = {
2016-07-04: 264464,
2016-07-05: 266458,
2016-07-07: 272720,
2016-07-08: 274352,
2016-07-11: 290110,
2016-07-12: 283604,
2016-07-14: 290356,
2016-07-19: 298452,
2016-07-22: 301793,
2016-07-24: 308439,
2016-07-25: 311762,
2016-07-27: 315518,
2016-07-28: 317712,
2016-07-29: 322961,
2016-07-30: 312415,
2016-07-31: 322962,
2016-08-02: 328265,
2016-08-06: 322963,
2016-08-08: 341632,
2016-08-15: 354271,
2016-08-16: 358108,
2016-08-26: 380486,
2016-08-27: 380495,
2016-08-28: 385578,
2016-08-29: 388026,
2016-08-30: 391542,
2016-09-03: 385575,
2016-09-04: 417260,
2016-09-05: 413816,
2016-09-06: 417249,
2016-09-07: 417244,
2016-09-08: 420326,
2016-09-17: 403546,
}

and I have an array

const daysToCheck = [
  "2016-09-01",
  "2016-09-02",
  "2016-09-03",
  "2016-09-04",
  "2016-09-05",
  "2016-09-06",
  "2016-09-07",
  "2016-09-08",
];

I want to find out if each of the items in the array exists in the keys of the object and how many of the items of the array are found in the keys of the object.

what does not work?

Nina Scholz
– Nina Scholz

2020-10-11 15:03:15 +00:00
Commented Oct 11, 2020 at 15:03 — Nina Scholz
– Nina Scholz, Commented Oct 11, 2020 at 15:03
What have you tried so far?

daniloxxv
– daniloxxv

2020-10-11 15:03:37 +00:00
Commented Oct 11, 2020 at 15:03 — daniloxxv
– daniloxxv, Commented Oct 11, 2020 at 15:03

Dragonsnap · Accepted Answer · 2020-10-11 15:12:30Z

1

You can find the intersection of two arrays using .filter method. Easier way of doing than what was proposed above.

let arr = Object.keys(Obj).filter( value => daysToCheck.includes(value));

Object.keys(Obj) extracts the keys of the Obj object, and the .filter return an array with values that are both in daysToCheck and Obj.

answered Oct 11, 2020 at 15:12

Dragonsnap

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Comments

ushka1 · Accepted Answer · 2020-10-11 15:05:18Z

Use reduce function on array and for each iteration, check if Obj has the value for the current array element. If it has then increment the accumulator value by one.

const Obj = {
  "2016-07-04": 264464,
  "2016-07-05": 266458,
  "2016-07-07": 272720,
  "2016-07-08": 274352,
  "2016-07-11": 290110,
  "2016-07-12": 283604,
  "2016-07-14": 290356,
  "2016-07-19": 298452,
  "2016-07-22": 301793,
  "2016-07-24": 308439,
  "2016-07-25": 311762,
  "2016-07-27": 315518,
  "2016-07-28": 317712,
  "2016-07-29": 322961,
  "2016-07-30": 312415,
  "2016-07-31": 322962,
  "2016-08-02": 328265,
  "2016-08-06": 322963,
  "2016-08-08": 341632,
  "2016-08-15": 354271,
  "2016-08-16": 358108,
  "2016-08-26": 380486,
  "2016-08-27": 380495,
  "2016-08-28": 385578,
  "2016-08-29": 388026,
  "2016-08-30": 391542,
  "2016-09-03": 385575,
  "2016-09-04": 417260,
  "2016-09-05": 413816,
  "2016-09-06": 417249,
  "2016-09-07": 417244,
  "2016-09-08": 420326,
  "2016-09-17": 403546,
}
  
const daysToCheck = [
  "2016-09-01",
  "2016-09-02",
  "2016-09-03",
  "2016-09-04",
  "2016-09-05",
  "2016-09-06",
  "2016-09-07",
  "2016-09-08",
];

const keysInArray = daysToCheck.reduce((acc, cur) => {
  if (Obj[cur]) {
    acc++;
  }

  return acc;
}, 0);

console.log(keysInArray);

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