How to Calculate the Time Difference Between Two Timestamps in JavaScript?

Determining the Time Difference Between Two Timestamps in JavaScript

How to Calculate the Time Difference

To calculate the time difference between two timestamps in JavaScript, you can leverage the Date object's subtraction operation.

Step 1: Convert Timestamps to Date Objects

First, create Date objects from the two timestamps. Since JavaScript does not provide a native method for parsing time strings, you can use arbitrary date components and set the specified time and UTC timezone:

let time1 = "09:00";
let time2 = "17:00";

let date1 = new Date(`2000-01-01T${time1}Z`);
let date2 = new Date(`2000-01-01T${time2}Z`);

Step 2: Handle Midnight Crossings (Optional)

In cases where the times are on opposite sides of midnight, adjust the timestamp with a later date to avoid incorrect subtraction results:

if (date2 < date1) {
  date2.setDate(date2.getDate() + 1);
}

Step 3: Subtract Timestamps

Subtract the earlier timestamp from the later timestamp to obtain the time difference, stored in milliseconds:

let diff = date2 - date1;
console.log(diff); // Output: 28800000 (8 hours)

Example Output

For the given example, where time1 is "09:00" and time2 is "17:00," the output will be 28800000 milliseconds, which translates to an 8-hour difference.

By following these steps, you can accurately determine the time difference between two timestamps in JavaScript. This calculation is useful in various scenarios, such as tracking time intervals or creating dynamic date-time functionalities.

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