Demo Extending The JavaScript Date Object with User Defined Methods

Read the original Digital Web article Extending The JavaScript Date Object with User Defined Methods by Lawrence O'Sullivan.

The methods are grouped by how they act on the date and whether they need addtional information. You can change the start date, number to add, and enddate. Rather than using several buttons there is just one per section. Similarly, there's just one field for the number of days, weekdays, weeks, months, and years to add to the start date. The number entered is used as the appropriate units for the method.

Starting Date

Year: Month: Date: Hour: Min: Sec:

Methods Returning Date Information

Method	Return Value
getFullDay
getDayAbbr
getFullMonth
getMonthAbbr
to12HourTimeString
to24HourTimeString
lastday
getDayOfYear

Show Date Info

Methods Adding to Dates

Enter a number for days, weeks, etc. to add to the start date.

Number to Add:

Method	New Date
addDays
addWeekDays
addWeeks
addMonths
addYears

Add to Date

End Date

Year: Month: Date:

The following methods require two dates. The start date above is used with the end date. The call is startDate.method(endDate);

Difference Between Two Dates

Method	Return Value
getDaysBetween
getWeekDays
getMonthsBetween*
getYearsBetween*

Calculate

Dates of Same Day Each Week Between Dates

Method	Week Day	Results
sameDayEachWeek	Sunday Monday Tuesday Wednesday Thursday Friday Saturday

Calculate

The method lastday() is used to prevent the user from entering a day value that exceeds the number of days in the month. And an additional method, toCustomString() is used to format the results for sameDayEachWeek() and has been added to the download file.

I hope you find this useful.

* The results were rounded to two decimals using toFixed.