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Getting the Max/Min Dates in an Array of Objects with JavaScript

ReadTime: 4 minutes

Buckle up Javascript Chrononauts 🚀⏲, in this blogpost we will explore how to find maximum and minimum dates in an array of Javascript objects.

The Date Object

The Date object in JavaScript encapsulates date and time functionality.

Key methods:

  • getFullYear(): Retrieves the year.

  • getMonth(): Retrieves the month (0-11).

  • getDate(): Retrieves the day of the month.

  • getHours(), getMinutes(), getSeconds(): Retrieves the respective time components.

  • setFullYear(), setMonth(), setDate(): Sets the corresponding date components.

Important Constructors:

Current Date and Time:

javascript
let currentDate = new Date();
console.log("Current Date and Time:", currentDate);
Understanding default Date constructor

Specifying a Date String:

javascript
let specificDate = new Date('2022-12-31T23:59:59');
console.log("Specific Date:", specificDate);
Creating Date with custom Date String

Using Year, Month, and Day:

javascript
let customDate = new Date(2022, 11, 31); // Month is zero-based
console.log("Custom Date:", customDate);
Creating Date with custom Year, Month and Day strings

Using Year, Month, Day, Hour, Minute, and Second:

javascript
let customDateTime = new Date(2022, 11, 31, 23, 59, 59);
console.log("Custom Date and Time:", customDateTime);
Creating Date with custom Year, Month, Day, Hour, Minute, Second strings

Using Epoch Time (Milliseconds Since 1970-01-01):

javascript
let epochTimeDate = new Date(1640995200000); // January 1, 2022
console.log("Epoch Time Date:", epochTimeDate);
Creating Date with custom custom epoch

Using Another Date Object:

javascript
let originalDate = new Date('2022-01-01');
let copiedDate = new Date(originalDate);
console.log("Copied Date:", copiedDate);
Creating date object using another Date object

Using Map and Math.max()/Math.min()

javascript
let dates = [
  { date: new Date('2022-01-01') },
  { date: new Date('2022-02-15') },
  { date: new Date('2022-03-10') }
];

let maxDate = new Date(Math.max(...dates.map(obj => obj.date.getTime())));
let minDate = new Date(Math.min(...dates.map(obj => obj.date.getTime())));

console.log("Max Date:", maxDate);
console.log("Min Date:", minDate);
Using map with Math.max and Math.min to get max min Dates

Explanation:

  • The dates array contains objects with a date property, each holding a JavaScript Date object.
  • dates.map(obj => obj.date.getTime()) extracts the time in milliseconds for each date using the map function. This results in an array of milliseconds.
  • Math.max(…millisecondsArray) and Math.min(…millisecondsArray) find the maximum and minimum values in the array of milliseconds, respectively.
  • new Date(maximumMilliseconds) and new Date(minimumMilliseconds) create Date objects using the maximum and minimum milliseconds found.
  • The final console.log statements display the maximum and minimum dates.

🧪Practice Coding Problem: Temporal Challenge

In the spirit of Test Driven Development ( 😁), lets test our understanding by solving a problem.

Find the sum of milliseconds between the maximum and minimum dates in the given Dates array.

javascript
// Temporal Challenge Question:
let dates = [
  { date: new Date('2022-01-01') },
  { date: new Date('2022-02-15') },
  { date: new Date('2022-03-10') }
];

/**
* Find the sum of milliseconds between
* the maximum and minimum dates in the array.
*/
function calculateTimeDifference(datesArray) {
  // > > > 👉 Write code here 👈 < < <
}

// User fills in the method
let timeBenderResult = calculateTimeDifference(dates);
console.log("Time Bender Result:", timeBenderResult);
Problem Code

Please attempt before seeing the Answer:

Solution
javascript
// Temporal Challenge Solution:
function calculateTimeDifference(datesArray) {
  let maxDate = new Date(Math.max(...datesArray.map(obj => obj.date.getTime())));
  let minDate = new Date(Math.min(...datesArray.map(obj => obj.date.getTime())));

  let timeDifference = maxDate.getTime() - minDate.getTime();
  return timeDifference;
}
Solution Code

Explanation:

  • calculateTimeDifference function takes an array of date objects as a parameter, finds the maximum and minimum dates using the map, Math.max, and Math.min techniques, calculates the time difference, and returns the result.

BTW, do you know why the JavaScript date refuse to go to the party? It heard they needed a timestamp, not a time-stampede. 😉

Happy coding 🚀!

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