What is the best way to find common elements in two arrays?

Question

What is the best way to find common elements in two arrays?

I have two arrays and I am trying to compare them in order to find the matching values only.

For instance, both arrays contain the date 2023/03/07, which is the value that should be returned.

I haven't come across a solution for this yet. What would be the most efficient way to identify the similarities?

var array1 = ["2023/03/07", "2023/03/17", "2023/03/27"];
var array2 = [];
var startDate = "2023/03/05";
var endDate = "2023/03/15";
var dateMove = new Date(startDate);
var strDate = startDate;

while (strDate < endDate) {
  var strDate = dateMove.toISOString().slice(0, 10);
  array2.push(strDate);
  dateMove.setDate(dateMove.getDate() + 1);
}

found = array1.find((val, index) => {
  return array2.includes(val);
});

console.log(found);
// if value in array1 is equal to value in array2 then return match: 2023/03/07

javascript arrays datetime

Answer 1

Answer №1

The toISOString() method requires dashes (-) as the separator:

YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ

By replacing slashes with dashes in the array, startDate, and endDate variables, the code will function correctly:

var array1 = ["2023-03-07", "2023-03-17", "2023-03-27"];
var array2 = [];
var startDate = "2023-03-05";
var endDate = "2023-03-15";
var dateMove = new Date(startDate);
var strDate = startDate;

while (strDate < endDate) {
  var strDate = dateMove.toISOString().slice(0, 10);
  array2.push(strDate);
  dateMove.setDate(dateMove.getDate() + 1);
}

found = array1.find((val, index) => {
  return array2.includes(val);
});

console.log(found);

Answer 2

The toISOString() method requires dashes (-) as the separator:

YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ

By replacing slashes with dashes in the array, startDate, and endDate variables, the code will function correctly:

var array1 = ["2023-03-07", "2023-03-17", "2023-03-27"];
var array2 = [];
var startDate = "2023-03-05";
var endDate = "2023-03-15";
var dateMove = new Date(startDate);
var strDate = startDate;

while (strDate < endDate) {
  var strDate = dateMove.toISOString().slice(0, 10);
  array2.push(strDate);
  dateMove.setDate(dateMove.getDate() + 1);
}

found = array1.find((val, index) => {
  return array2.includes(val);
});

console.log(found);

Answer 3

Answer №2

If there are multiple values found, your current code will not work as the result of find is being assigned to found. It's important to note that find returns the first result found. Refer to the documentation for more information.

To address this issue, update the code to use Array.filter instead:

found = array1.filter((val, index) => {
  return array2.includes(val);
});

In addition, I would like to highlight a helpful library called luxon, which simplifies working with dates:

var { DateTime, Interval } = require('luxon');

var array1 = ["2023-03-07", "2023-03-17", "2023-03-27"];
var startDate = "2023-03-05";
var endDate = "2023-03-15";

const interval = Interval.fromDateTimes(DateTime.fromISO(startDate), DateTime.fromISO(endDate));

var found = array1.filter(date => interval.contains(DateTime.fromISO(date)));

console.log(found);

If you prefer to maintain the input format using slashes instead of dashes, Luxon allows you to create DateTime objects using fromFormat.

Answer 4

If there are multiple values found, your current code will not work as the result of find is being assigned to found. It's important to note that find returns the first result found. Refer to the documentation for more information.

To address this issue, update the code to use Array.filter instead:

found = array1.filter((val, index) => {
  return array2.includes(val);
});

In addition, I would like to highlight a helpful library called luxon, which simplifies working with dates:

var { DateTime, Interval } = require('luxon');

var array1 = ["2023-03-07", "2023-03-17", "2023-03-27"];
var startDate = "2023-03-05";
var endDate = "2023-03-15";

const interval = Interval.fromDateTimes(DateTime.fromISO(startDate), DateTime.fromISO(endDate));

var found = array1.filter(date => interval.contains(DateTime.fromISO(date)));

console.log(found);

If you prefer to maintain the input format using slashes instead of dashes, Luxon allows you to create DateTime objects using fromFormat.

What is the best way to find common elements in two arrays?

Answer №1

Answer №2

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