How Can I Add Hours to a JavaScript Date Object?

Extending Date Object with an "addHours" Function

While the JavaScript Date object lacks an add method, it's possible to create one with custom functionality.

Implementation

To add hours to a Date, follow these steps:

1. Convert hours to milliseconds: Multiply the number of hours by 60 minutes, then by 60 seconds, and finally by 1000 milliseconds.
2. Set the new time: Use setTime() to set the date to its current time plus the calculated milliseconds.
3. Return the modified date: Return this to allow for chaining of additional methods.

Date.prototype.addHours = function(h) {
  this.setTime(this.getTime() + (h*60*60*1000));
  return this;
}

Example Usage

const now = new Date();
const fourHoursLater = now.addHours(4); // 4 hours added to current date

Notes

• This implementation does not handle edge cases like adding negative hours or adding too many hours that would result in a date with an invalid date or month.
• The setTime() method can take a timestamp in milliseconds, which is why we convert hours to milliseconds before using it.

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