Momentjs date string add 5 days

Deep dive into moment.js

Moment.js offers a wide variety of operations to manipulate dates. The .add() function is one of the standouts as we can employ it to add to parts of the date. However, keep an eye on some important issues:

Modifying original moment.js objects

Contrary to common belief, when you manipulate a date object using .add(), the original date object also changes:

let initialDate = moment("YYYY-MM-DD");
let newDate = initialDate.add(5, 'days');

console.log(initialDate.format()); // PLOT TWIST: It's 5 days later too!. 📅
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No magic here, it's how moment.js works. To keep your original date pristine, use .clone() before manipulating:

let initialDate = moment("YYYY-MM-DD");
let newDate = initialDate.clone().add(5, 'days');

console.log(initialDate.format()); // Still at square one. 🎩
console.log(newDate.format());      // Now, it is 5 days later. 🎉
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Keep an eye on formatting

Moment.js defaults to ISO format after manipulation, which could cause format inconsistency in your application. To ensure consistent date presentation, specify the desired format in the .format() call like below:

var formattedNewDate = moment("YYYY-MM-DD").add(5, 'days').format('DD.MM.YYYY');
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Alternatives to moment.js

Although moment.js is the go-to for many developers, other libraries like Day.js or date-fns offer a lighter footprint with similar features. Consider them depending on the case in hand.

Navigating time zones and daylight saving

Understanding how moment.js handles time zones and daylight saving time is important:

Time zones handling

Adding days across time zones? Be careful, you might end up in the wrong movie screening:

let movieNight = moment.tz("YYYY-MM-DD", "America/New_York");
let newDate = movieNight.clone().add(5, 'days').tz("America/Los_Angeles");

// Welcome to the Future. But did we miss the movie? 🎥 🍿
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DST shenanigans

DST changes can cause the "Day That Never Ends," or you might end up with "25-Hour Days." Sounds like fun, but your calculations might not agree:

let partyDate = moment.tz("YYYY-MM-DD", "Europe/London");
partyDate.add(5, 'days'); // Could be longer or shorter, bring extra snacks! 🥳 🎈
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As DST changes adjust our clocks, moment.js cleverly adjusts time accordingly, but verifying your results is highly recommended.

Optimize your code

The power of brevity in code should not be underestimated. Literal objects and shorthand notation can provide more clarity and readability in moment.js:

moment().add(5, 'd');               // 'd' is the new 'days' 🕺
moment().add({ days: 5 });          // "5 days, good sir!" 🎩
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