检查数组中有多少元素作为javascript对象中的键存在

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.

Answer 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 value s that are both in daysToCheck and Obj .

Answer 2

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);