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

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:

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

Specifying a Date String:

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

Using Year, Month, and Day:

let customDate = new Date(2022, 11, 31); // Month is zero-based
console.log("Custom Date:", customDate);

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

let customDateTime = new Date(2022, 11, 31, 23, 59, 59);
console.log("Custom Date and Time:", customDateTime);

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

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

Using Another Date Object:

let originalDate = new Date('2022-01-01');
let copiedDate = new Date(originalDate);
console.log("Copied Date:", copiedDate);

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

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);

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);

// 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;
}

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 🚀!