Get the difference between 2 dates in JavaScript?

Dodge the potential issues

In JavaScript, avoid common pitfalls in date calculations by keeping these handy tips in mind:

UTC Normalization: Switch dates to UTC to guarantee that DST doesn't skew the difference. Remember, time flies, but not always at one-hour intervals.

const utcDate1 = Date.UTC(date1.getFullYear(), date1.getMonth(), date1.getDate());
const utcDate2 = Date.UTC(date2.getFullYear(), date2.getMonth(), date2.getDate());
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Calculating complete days: Just want the full day's difference? Bypass those pesky hours, minutes, and seconds:

const startDate = new Date(date1.toDateString());
const endDate = new Date(date2.toDateString());
// We use Math.abs() to avoid time-travelling to negative days!
const fullDayDifference = Math.abs(endDate - startDate) / 86,400,000; 
console.log(fullDayDifference);
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Handling early birds: Ensure to diplomatically handle cases where the end date decides to arrive before the start date.

Enhance user experience with jQuery UI datepicker

Applying datepicker from jQuery UI can literally take your date calculations to new interactive heights. Automate calculations upon date selection with an onChange function.

$("#datepicker").datepicker({
  changeMonth: true,  // Changing months? Easy peasy lemon squeezy!
  changeYear: true,   // Or changing years? Just as breezy!
  onSelect: function(dateText) {
    // Perform calculations when a date is picked
  }
});
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And remember, always validate the inputs to escape from Unwanted Calculation Abyss (UCA).

Working Demo

Providing a working demo makes your calculations life-like with interactive snippets. Supplement your work with libraries like jQuery and jQuery UI for extended functionality, and to raise a few brows!

Factors for robust date computations

Here are some secret ingredients for efficient date difference computations:

Leap years: Tip: Working with Date objects solves the Leap-Yearheadache for you. Yes, JavaScript got your back!

Month boundaries: Strictly adhere to each month's boundary when calculating differences. Remember, every day counts!

Peak performance: Too many date calculations bogging you down? Opt for a math-based approach, who said programmers aren't good at math?

Result validation: Keep the output neat by parsing results as whole days without fractions. Because no one likes half a day-off, right?

Different formats – Not a challenge!

Encountering different date formats? Make them uniform using the "mm/dd/yyyy" format:

// Remember! Moses didn't part the Red Sea to confuse date formats.
const dateFromString = new Date("mm/dd/yyyy");
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Avoid format mismatches and convert your strings to Date objects.