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addSeconds()

Adds or subtracts seconds from a Date object.

Syntax

addSeconds(dateObj, seconds)

Parameters

ParameterTypeRequiredDescription
dateObjDateYesThe base Date object
secondsnumberYesNumber of seconds to add (positive) or subtract (negative)

Returns

Date - A new Date object with the specified number of seconds added or subtracted

Basic Examples

Adding and Subtracting Seconds

import { addSeconds } from 'date-and-time';


const date = new Date(2024, 7, 15, 14, 30, 45, 123);  // August 15, 2024 14:30:45.123


// Add seconds
const future = addSeconds(date, 30);
console.log(future);  // August 15, 2024 14:31:15.123


// Subtract seconds
const past = addSeconds(date, -20);
console.log(past);  // August 15, 2024 14:30:25.123

Use Cases

Countdown Timers

function createCountdown(duration: number): { start: Date, end: Date, remaining: () => number } {
  const start = new Date();
  const end = addSeconds(start, duration);


  return {
    start,
    end,
    remaining: () => Math.max(0, Math.floor((end.getTime() - Date.now()) / 1000))
  };
}


const countdown = createCountdown(300); // 5 minute countdown
console.log(`Countdown ends at: ${countdown.end.toLocaleTimeString()}`);
console.log(`Time remaining: ${countdown.remaining()} seconds`);


// Use in a timer
const updateCountdown = () => {
  const remaining = countdown.remaining();
  if (remaining > 0) {
    console.log(`${remaining} seconds left`);
    setTimeout(updateCountdown, 1000);
  } else {
    console.log('Time up!');
  }
};


updateCountdown();

Precise Time Intervals

function generateTimeIntervals(startTime: Date, intervalSeconds: number, count: number): Date[] {
  const intervals: Date[] = [];
  let currentTime = new Date(startTime);


  for (let i = 0; i < count; i++) {
    intervals.push(new Date(currentTime));
    currentTime = addSeconds(currentTime, intervalSeconds);
  }


  return intervals;
}


const start = new Date(2024, 7, 15, 12, 0, 0);  // August 15, 2024 12:00:00
const intervals = generateTimeIntervals(start, 15, 8);  // Every 15 seconds, 8 times


console.log(intervals);
// [12:00:00, 12:00:15, 12:00:30, 12:00:45, 12:01:00, 12:01:15, 12:01:30, 12:01:45]

Immutability

addSeconds() does not modify the original Date object:

const originalDate = new Date(2024, 7, 15, 14, 30, 45);
const modifiedDate = addSeconds(originalDate, 120);


console.log(originalDate);  // August 15, 2024 14:30:45 (unchanged)
console.log(modifiedDate);  // August 15, 2024 14:32:45 (new object);

See Also